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	$79.55	11.167%	$88.4333	$88.43	$88.45	$88.40
Purchase #2	$61.27	9.184%	$66.897	$66.90	$66.90	$66.90
Purchase #3	$212.73	8.171%	$230.1122	$230.11	$230.10	$230.10
Purchase #4	$156.35	10.220%	$172.329	$172.33	$172.35	$172.30
Purchase #5	$225.90	12.563%	$254.2798	$254.28	$254.30	$254.30
Purchase #6	$215.83	9.609%	$236.5691	$236.57	$236.55	$236.60
Purchase #7	$90.98	5.190%	$95.7019	$95.70	$95.70	$95.70
7 purchase totals =	$1,042.61		$1,144.3223	$1,144.32	$1,144.35	$1,144.30