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	$194.38	9.142%	$212.1502	$212.15	$212.15	$212.20
Purchase #2	$249.45	10.198%	$274.8889	$274.89	$274.90	$274.90
Purchase #3	$205.61	9.862%	$225.8873	$225.89	$225.90	$225.90
Purchase #4	$223.33	11.300%	$248.5663	$248.57	$248.55	$248.60
Purchase #5	$158.81	9.116%	$173.2871	$173.29	$173.30	$173.30
Purchase #6	$63.70	12.490%	$71.6561	$71.66	$71.65	$71.70
Purchase #7	$246.45	3.564%	$255.2335	$255.23	$255.25	$255.20
7 purchase totals =	$1,341.73		$1,461.6694	$1,461.68	$1,461.70	$1,461.80