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	$212.73	13.537%	$241.5273	$241.53	$241.55	$241.50
Purchase #2	$182.34	11.359%	$203.052	$203.05	$203.05	$203.10
Purchase #3	$226.54	13.196%	$256.4342	$256.43	$256.45	$256.40
Purchase #4	$47.82	5.722%	$50.5563	$50.56	$50.55	$50.60
Purchase #5	$180.93	5.277%	$190.4777	$190.48	$190.50	$190.50
Purchase #6	$244.44	4.376%	$255.1367	$255.14	$255.15	$255.10
Purchase #7	$44.71	7.479%	$48.0539	$48.05	$48.05	$48.10
7 purchase totals =	$1,139.51		$1,245.2381	$1,245.24	$1,245.30	$1,245.30