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	$198.80	8.688%	$216.0717	$216.07	$216.05	$216.10
Purchase #2	$132.85	7.749%	$143.1445	$143.14	$143.15	$143.10
Purchase #3	$32.34	4.251%	$33.7148	$33.71	$33.70	$33.70
Purchase #4	$114.29	11.785%	$127.7591	$127.76	$127.75	$127.80
Purchase #5	$50.56	13.551%	$57.4114	$57.41	$57.40	$57.40
Purchase #6	$39.89	8.232%	$43.1737	$43.17	$43.15	$43.20
Purchase #7	$234.79	8.810%	$255.475	$255.48	$255.50	$255.50
7 purchase totals =	$803.52		$876.7502	$876.74	$876.70	$876.80