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	$250.37	7.748%	$269.7687	$269.77	$269.75	$269.80
Purchase #2	$60.72	7.617%	$65.345	$65.35	$65.35	$65.30
Purchase #3	$161.51	8.385%	$175.0526	$175.05	$175.05	$175.10
Purchase #4	$223.35	6.762%	$238.4529	$238.45	$238.45	$238.50
Purchase #5	$131.72	6.277%	$139.9881	$139.99	$140.00	$140.00
Purchase #6	$116.95	11.804%	$130.7548	$130.75	$130.75	$130.80
Purchase #7	$37.47	8.164%	$40.5291	$40.53	$40.55	$40.50
7 purchase totals =	$982.09		$1,059.8912	$1,059.89	$1,059.90	$1,060.00