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	$114.77	10.323%	$126.6177	$126.62	$126.60	$126.60
Purchase #2	$65.70	8.634%	$71.3725	$71.37	$71.35	$71.40
Purchase #3	$205.53	11.434%	$229.0303	$229.03	$229.05	$229.00
Purchase #4	$153.52	11.495%	$171.1671	$171.17	$171.15	$171.20
Purchase #5	$185.93	4.770%	$194.7989	$194.80	$194.80	$194.80
Purchase #6	$131.41	6.460%	$139.8991	$139.90	$139.90	$139.90
Purchase #7	$64.46	9.579%	$70.6346	$70.63	$70.65	$70.60
7 purchase totals =	$921.32		$1,003.5202	$1,003.52	$1,003.50	$1,003.50