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	$133.27	4.717%	$139.5563	$139.56	$139.55	$139.60
Purchase #2	$53.62	7.763%	$57.7825	$57.78	$57.80	$57.80
Purchase #3	$48.34	12.692%	$54.4753	$54.48	$54.50	$54.50
Purchase #4	$139.30	11.563%	$155.4073	$155.41	$155.40	$155.40
Purchase #5	$109.59	13.306%	$124.172	$124.17	$124.15	$124.20
Purchase #6	$40.60	13.137%	$45.9336	$45.93	$45.95	$45.90
Purchase #7	$109.32	8.436%	$118.5422	$118.54	$118.55	$118.50
7 purchase totals =	$634.04		$695.8692	$695.87	$695.90	$695.90