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	$129.34	13.586%	$146.9121	$146.91	$146.90	$146.90
Purchase #2	$112.72	4.807%	$118.1385	$118.14	$118.15	$118.10
Purchase #3	$29.82	7.719%	$32.1218	$32.12	$32.10	$32.10
Purchase #4	$124.81	4.766%	$130.7584	$130.76	$130.75	$130.80
Purchase #5	$126.29	5.487%	$133.2195	$133.22	$133.20	$133.20
Purchase #6	$169.56	11.119%	$188.4134	$188.41	$188.40	$188.40
Purchase #7	$163.86	13.230%	$185.5387	$185.54	$185.55	$185.50
7 purchase totals =	$856.40		$935.1024	$935.10	$935.05	$935.00