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	$40.33	3.428%	$41.7125	$41.71	$41.70	$41.70
Purchase #2	$85.64	5.207%	$90.0993	$90.10	$90.10	$90.10
Purchase #3	$249.32	6.495%	$265.5133	$265.51	$265.50	$265.50
Purchase #4	$209.60	7.580%	$225.4877	$225.49	$225.50	$225.50
Purchase #5	$226.99	7.764%	$244.6135	$244.61	$244.60	$244.60
Purchase #6	$56.65	9.858%	$62.2346	$62.23	$62.25	$62.20
Purchase #7	$149.55	10.720%	$165.5818	$165.58	$165.60	$165.60
7 purchase totals =	$1,018.08		$1,095.2427	$1,095.23	$1,095.25	$1,095.20