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	$58.29	13.406%	$66.1044	$66.10	$66.10	$66.10
Purchase #2	$235.86	8.645%	$256.2501	$256.25	$256.25	$256.30
Purchase #3	$151.85	5.662%	$160.4477	$160.45	$160.45	$160.40
Purchase #4	$211.52	5.320%	$222.7729	$222.77	$222.75	$222.80
Purchase #5	$180.34	5.844%	$190.8791	$190.88	$190.90	$190.90
Purchase #6	$203.28	3.278%	$209.9435	$209.94	$209.95	$209.90
Purchase #7	$168.59	12.362%	$189.4311	$189.43	$189.45	$189.40
7 purchase totals =	$1,209.73		$1,295.8288	$1,295.82	$1,295.85	$1,295.80