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	$43.73	3.153%	$45.1088	$45.11	$45.10	$45.10
Purchase #2	$66.66	7.724%	$71.8088	$71.81	$71.80	$71.80
Purchase #3	$146.81	8.860%	$159.8174	$159.82	$159.80	$159.80
Purchase #4	$158.56	7.368%	$170.2427	$170.24	$170.25	$170.20
Purchase #5	$248.71	6.573%	$265.0577	$265.06	$265.05	$265.10
Purchase #6	$175.99	11.213%	$195.7238	$195.72	$195.70	$195.70
Purchase #7	$187.89	8.482%	$203.8268	$203.83	$203.85	$203.80
7 purchase totals =	$1,028.35		$1,111.5860	$1,111.59	$1,111.55	$1,111.50