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	$130.85	11.824%	$146.3217	$146.32	$146.30	$146.30
Purchase #2	$212.78	9.798%	$233.6282	$233.63	$233.65	$233.60
Purchase #3	$10.57	8.188%	$11.4355	$11.44	$11.45	$11.40
Purchase #4	$38.37	11.410%	$42.748	$42.75	$42.75	$42.70
Purchase #5	$190.61	9.301%	$208.3386	$208.34	$208.35	$208.30
Purchase #6	$221.79	4.290%	$231.3048	$231.30	$231.30	$231.30
Purchase #7	$83.48	6.813%	$89.1675	$89.17	$89.15	$89.20
7 purchase totals =	$888.45		$962.9443	$962.95	$962.95	$962.80