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	$140.84	10.704%	$155.9155	$155.92	$155.90	$155.90
Purchase #2	$194.81	3.415%	$201.4628	$201.46	$201.45	$201.50
Purchase #3	$40.67	5.371%	$42.8544	$42.85	$42.85	$42.90
Purchase #4	$36.58	9.542%	$40.0705	$40.07	$40.05	$40.10
Purchase #5	$200.32	11.763%	$223.8836	$223.88	$223.90	$223.90
Purchase #6	$212.41	10.394%	$234.4879	$234.49	$234.50	$234.50
Purchase #7	$46.89	4.776%	$49.1295	$49.13	$49.15	$49.10
7 purchase totals =	$872.52		$947.8042	$947.80	$947.80	$947.90