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	$95.85	4.604%	$100.2629	$100.26	$100.25	$100.30
Purchase #2	$69.85	10.431%	$77.1361	$77.14	$77.15	$77.10
Purchase #3	$5.70	13.121%	$6.4479	$6.45	$6.45	$6.40
Purchase #4	$118.47	9.516%	$129.7436	$129.74	$129.75	$129.70
Purchase #5	$56.50	10.405%	$62.3788	$62.38	$62.40	$62.40
Purchase #6	$66.32	8.485%	$71.9473	$71.95	$71.95	$71.90
Purchase #7	$50.61	9.713%	$55.5257	$55.53	$55.55	$55.50
7 purchase totals =	$463.30		$503.4423	$503.45	$503.50	$503.30