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	$160.72	10.457%	$177.5265	$177.53	$177.55	$177.50
Purchase #2	$229.99	11.251%	$255.8662	$255.87	$255.85	$255.90
Purchase #3	$34.28	10.115%	$37.7474	$37.75	$37.75	$37.70
Purchase #4	$50.89	9.733%	$55.8431	$55.84	$55.85	$55.80
Purchase #5	$118.45	7.510%	$127.3456	$127.35	$127.35	$127.30
Purchase #6	$23.49	11.574%	$26.2087	$26.21	$26.20	$26.20
Purchase #7	$61.56	10.311%	$67.9075	$67.91	$67.90	$67.90
7 purchase totals =	$679.38		$748.4450	$748.46	$748.45	$748.30