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	$148.83	8.525%	$161.5178	$161.52	$161.50	$161.50
Purchase #2	$222.41	10.332%	$245.3894	$245.39	$245.40	$245.40
Purchase #3	$41.34	11.143%	$45.9465	$45.95	$45.95	$45.90
Purchase #4	$136.83	10.868%	$151.7007	$151.70	$151.70	$151.70
Purchase #5	$100.51	10.530%	$111.0937	$111.09	$111.10	$111.10
Purchase #6	$52.95	8.701%	$57.5572	$57.56	$57.55	$57.60
Purchase #7	$223.35	7.241%	$239.5228	$239.52	$239.50	$239.50
7 purchase totals =	$926.22		$1,012.7281	$1,012.73	$1,012.70	$1,012.70