Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.37	6.705%	$184.9945	$184.99	$185.00	$185.00
Purchase #2	$34.71	13.860%	$39.5208	$39.52	$39.50	$39.50
Purchase #3	$102.47	9.850%	$112.5633	$112.56	$112.55	$112.60
Purchase #4	$164.83	7.433%	$177.0818	$177.08	$177.10	$177.10
Purchase #5	$99.50	11.724%	$111.1654	$111.17	$111.15	$111.20
Purchase #6	$158.96	3.630%	$164.7302	$164.73	$164.75	$164.70
Purchase #7	$115.63	10.207%	$127.4324	$127.43	$127.45	$127.40
7 purchase totals =	$849.47		$917.4884	$917.48	$917.50	$917.50