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	$191.52	11.546%	$213.6329	$213.63	$213.65	$213.60
Purchase #2	$112.45	3.712%	$116.6241	$116.62	$116.60	$116.60
Purchase #3	$65.70	9.534%	$71.9638	$71.96	$71.95	$72.00
Purchase #4	$165.87	10.634%	$183.5086	$183.51	$183.50	$183.50
Purchase #5	$145.42	8.832%	$158.2635	$158.26	$158.25	$158.30
Purchase #6	$36.35	12.695%	$40.9646	$40.96	$40.95	$41.00
Purchase #7	$59.71	3.629%	$61.8769	$61.88	$61.90	$61.90
7 purchase totals =	$777.02		$846.8344	$846.82	$846.80	$846.90