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	$243.74	11.733%	$272.338	$272.34	$272.35	$272.30
Purchase #2	$77.28	10.430%	$85.3403	$85.34	$85.35	$85.30
Purchase #3	$218.37	11.697%	$243.9127	$243.91	$243.90	$243.90
Purchase #4	$217.98	10.760%	$241.4346	$241.43	$241.45	$241.40
Purchase #5	$102.56	6.433%	$109.1577	$109.16	$109.15	$109.20
Purchase #6	$141.66	11.809%	$158.3886	$158.39	$158.40	$158.40
Purchase #7	$230.59	8.177%	$249.4453	$249.45	$249.45	$249.40
7 purchase totals =	$1,232.18		$1,360.0172	$1,360.02	$1,360.05	$1,359.90