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	$53.96	8.122%	$58.3426	$58.34	$58.35	$58.30
Purchase #2	$239.31	4.804%	$250.8065	$250.81	$250.80	$250.80
Purchase #3	$39.26	6.694%	$41.8881	$41.89	$41.90	$41.90
Purchase #4	$31.50	4.168%	$32.8129	$32.81	$32.80	$32.80
Purchase #5	$247.29	8.836%	$269.1405	$269.14	$269.15	$269.10
Purchase #6	$166.88	11.317%	$185.7658	$185.77	$185.75	$185.80
Purchase #7	$234.29	11.707%	$261.7183	$261.72	$261.70	$261.70
7 purchase totals =	$1,012.49		$1,100.4747	$1,100.48	$1,100.45	$1,100.40