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	$209.98	3.324%	$216.9597	$216.96	$216.95	$217.00
Purchase #2	$118.34	13.755%	$134.6177	$134.62	$134.60	$134.60
Purchase #3	$55.48	3.454%	$57.3963	$57.40	$57.40	$57.40
Purchase #4	$41.91	10.594%	$46.3499	$46.35	$46.35	$46.30
Purchase #5	$117.82	7.664%	$126.8497	$126.85	$126.85	$126.80
Purchase #6	$240.25	12.103%	$269.3275	$269.33	$269.35	$269.30
Purchase #7	$85.95	4.332%	$89.6734	$89.67	$89.65	$89.70
7 purchase totals =	$869.73		$941.1742	$941.18	$941.15	$941.10