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	$132.76	3.248%	$137.072	$137.07	$137.05	$137.10
Purchase #2	$116.26	9.259%	$127.0245	$127.02	$127.00	$127.00
Purchase #3	$195.71	11.525%	$218.2656	$218.27	$218.25	$218.30
Purchase #4	$146.47	8.470%	$158.876	$158.88	$158.90	$158.90
Purchase #5	$67.43	6.263%	$71.6531	$71.65	$71.65	$71.70
Purchase #6	$68.54	3.816%	$71.1555	$71.16	$71.15	$71.20
Purchase #7	$140.77	13.729%	$160.0963	$160.10	$160.10	$160.10
7 purchase totals =	$867.94		$944.1430	$944.15	$944.10	$944.30