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	$28.77	12.109%	$32.2538	$32.25	$32.25	$32.30
Purchase #2	$37.52	3.664%	$38.8947	$38.89	$38.90	$38.90
Purchase #3	$238.42	7.671%	$256.7092	$256.71	$256.70	$256.70
Purchase #4	$226.46	9.301%	$247.523	$247.52	$247.50	$247.50
Purchase #5	$149.40	5.387%	$157.4482	$157.45	$157.45	$157.40
Purchase #6	$166.51	8.115%	$180.0223	$180.02	$180.00	$180.00
Purchase #7	$222.37	7.391%	$238.8054	$238.81	$238.80	$238.80
7 purchase totals =	$1,069.45		$1,151.6566	$1,151.65	$1,151.60	$1,151.60