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	$165.62	12.191%	$185.8107	$185.81	$185.80	$185.80
Purchase #2	$90.85	10.624%	$100.5019	$100.50	$100.50	$100.50
Purchase #3	$239.38	10.344%	$264.1415	$264.14	$264.15	$264.10
Purchase #4	$195.51	8.433%	$211.9974	$212.00	$212.00	$212.00
Purchase #5	$175.65	11.781%	$196.3433	$196.34	$196.35	$196.30
Purchase #6	$207.56	7.512%	$223.1519	$223.15	$223.15	$223.20
Purchase #7	$134.90	10.307%	$148.8041	$148.80	$148.80	$148.80
7 purchase totals =	$1,209.47		$1,330.7508	$1,330.74	$1,330.75	$1,330.70