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	$223.46	13.252%	$253.0729	$253.07	$253.05	$253.10
Purchase #2	$73.52	5.444%	$77.5224	$77.52	$77.50	$77.50
Purchase #3	$238.47	10.508%	$263.5284	$263.53	$263.55	$263.50
Purchase #4	$240.65	6.480%	$256.2441	$256.24	$256.25	$256.20
Purchase #5	$240.95	13.244%	$272.8614	$272.86	$272.85	$272.90
Purchase #6	$60.69	9.635%	$66.5375	$66.54	$66.55	$66.50
Purchase #7	$67.41	5.513%	$71.1263	$71.13	$71.15	$71.10
7 purchase totals =	$1,145.15		$1,260.8930	$1,260.89	$1,260.90	$1,260.80