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	$116.84	9.425%	$127.8522	$127.85	$127.85	$127.90
Purchase #2	$192.33	10.594%	$212.7054	$212.71	$212.70	$212.70
Purchase #3	$115.86	10.580%	$128.118	$128.12	$128.10	$128.10
Purchase #4	$236.65	13.149%	$267.7671	$267.77	$267.75	$267.80
Purchase #5	$146.72	3.300%	$151.5618	$151.56	$151.55	$151.60
Purchase #6	$86.28	5.637%	$91.1436	$91.14	$91.15	$91.10
Purchase #7	$90.81	9.155%	$99.1237	$99.12	$99.10	$99.10
7 purchase totals =	$985.49		$1,078.2718	$1,078.27	$1,078.20	$1,078.30