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	$54.50	10.503%	$60.2241	$60.22	$60.20	$60.20
Purchase #2	$11.74	10.288%	$12.9478	$12.95	$12.95	$12.90
Purchase #3	$120.29	13.714%	$136.7866	$136.79	$136.80	$136.80
Purchase #4	$61.83	5.813%	$65.4242	$65.42	$65.40	$65.40
Purchase #5	$98.34	13.827%	$111.9375	$111.94	$111.95	$111.90
Purchase #6	$120.38	3.715%	$124.8521	$124.85	$124.85	$124.90
Purchase #7	$140.59	7.549%	$151.2031	$151.20	$151.20	$151.20
7 purchase totals =	$607.67		$663.3754	$663.37	$663.35	$663.30