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	$219.58	12.454%	$246.9265	$246.93	$246.95	$246.90
Purchase #2	$211.81	4.741%	$221.8519	$221.85	$221.85	$221.90
Purchase #3	$157.42	8.238%	$170.3883	$170.39	$170.40	$170.40
Purchase #4	$89.98	9.246%	$98.2996	$98.30	$98.30	$98.30
Purchase #5	$33.87	10.228%	$37.3342	$37.33	$37.35	$37.30
Purchase #6	$50.50	11.419%	$56.2666	$56.27	$56.25	$56.30
Purchase #7	$115.29	7.466%	$123.8976	$123.90	$123.90	$123.90
7 purchase totals =	$878.45		$954.9647	$954.97	$955.00	$955.00