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	$34.42	6.792%	$36.7578	$36.76	$36.75	$36.80
Purchase #2	$45.29	11.534%	$50.5137	$50.51	$50.50	$50.50
Purchase #3	$93.33	13.254%	$105.7	$105.70	$105.70	$105.70
Purchase #4	$55.42	11.196%	$61.6248	$61.62	$61.60	$61.60
Purchase #5	$96.86	7.521%	$104.1448	$104.14	$104.15	$104.10
Purchase #6	$159.54	11.733%	$178.2588	$178.26	$178.25	$178.30
Purchase #7	$71.27	6.803%	$76.1185	$76.12	$76.10	$76.10
7 purchase totals =	$556.13		$613.1184	$613.11	$613.05	$613.10