Is there a cash register obligation like in Austria?

In Germany there is no general cash register obligation, in contrast to Austria. You can use an open cash till any longer if you observe the requirements for them. (Take a Look at AEAO zu § 146 Nr. 3)

There is no legal obligation to use an electronic recording system.

Individual records can be made in the form of a cash register by the complete and detailed recording (see AEAO to Sections 146, No. 2.1.2 and 2.1.3). If a cash report is used to determine the daily draw, the individual recording can also be ensured by the ordered (e.B. numbered) collection of all cash documents.

If, for reasons of reasonableness, there is no obligation to record individual (see AEAO to Section 146, Point 2.2.2), the cash receipts must be proven at least on the basis of a cash report. In this case, it must always be assumed that the cash balance of the respective business day has been counted. At the close of business of the previous day, the cash balance and the cash deposits to be occupied by self-subsistence are deducted from this cash balance. Expenditure and cash withdrawals to be substantiated by self-proof shall be added.

A so-called "counting protocol" (listing the exact number of units of existing banknotes and coins) is not required(BFH decision of 16.12.2016, X B 41/16, BFH/NV 2017 p. 310), but facilitates proof of the actual counting.

Cash earnings and cash expenditures have to be recorded on a daily basis. If, exceptionally, cash receipts and cash expenses are not recorded until the next business day, this is still correct if compelling business reasons preclude a recording on the same day and it can be reliably taken from the records and documents how the intended cash balance has developed (see BFH judgment of 31.7.1974, I R 216/72, BStBl II p. 96). In the case of cash registers without sales personnel (so-called trust cash registers,.B e.g. vegetable sales at the edge of the field, ticket machines and vending machines for goods and services), there is no complaint if these are not counted daily, but only when emptying. Cash records must be such that an expert third party is always in a position to compare the debit stock with the actual holdings of the cash register(BFH judgment of 20.9.1989, X R 39/87, BStBl 1990 II p. 109). The VAT recording and retention obligations remain unaffected.