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	$212.58	10.140%	$234.1356	$234.14	$234.15	$234.10
Purchase #2	$52.42	13.400%	$59.4443	$59.44	$59.45	$59.40
Purchase #3	$56.58	10.827%	$62.7059	$62.71	$62.70	$62.70
Purchase #4	$180.37	10.655%	$199.5884	$199.59	$199.60	$199.60
Purchase #5	$92.52	9.810%	$101.5962	$101.60	$101.60	$101.60
Purchase #6	$146.73	7.559%	$157.8213	$157.82	$157.80	$157.80
Purchase #7	$184.76	3.348%	$190.9458	$190.95	$190.95	$190.90
7 purchase totals =	$925.96		$1,006.2375	$1,006.25	$1,006.25	$1,006.10