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	$130.45	8.519%	$141.563	$141.56	$141.55	$141.60
Purchase #2	$230.86	13.493%	$262.0099	$262.01	$262.00	$262.00
Purchase #3	$245.39	4.637%	$256.7687	$256.77	$256.75	$256.80
Purchase #4	$113.82	6.157%	$120.8279	$120.83	$120.85	$120.80
Purchase #5	$33.34	3.695%	$34.5719	$34.57	$34.55	$34.60
Purchase #6	$247.90	11.282%	$275.8681	$275.87	$275.85	$275.90
Purchase #7	$129.48	9.510%	$141.7935	$141.79	$141.80	$141.80
7 purchase totals =	$1,131.24		$1,233.4030	$1,233.40	$1,233.35	$1,233.50