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	$133.39	7.529%	$143.4329	$143.43	$143.45	$143.40
Purchase #2	$197.61	7.141%	$211.7213	$211.72	$211.70	$211.70
Purchase #3	$30.87	6.604%	$32.9087	$32.91	$32.90	$32.90
Purchase #4	$138.90	8.753%	$151.0579	$151.06	$151.05	$151.10
Purchase #5	$243.32	10.638%	$269.2044	$269.20	$269.20	$269.20
Purchase #6	$195.53	6.830%	$208.8847	$208.88	$208.90	$208.90
Purchase #7	$105.31	6.294%	$111.9382	$111.94	$111.95	$111.90
7 purchase totals =	$1,044.93		$1,129.1481	$1,129.14	$1,129.15	$1,129.10