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	$149.80	10.218%	$165.1066	$165.11	$165.10	$165.10
Purchase #2	$92.96	9.868%	$102.1333	$102.13	$102.15	$102.10
Purchase #3	$35.57	13.607%	$40.41	$40.41	$40.40	$40.40
Purchase #4	$127.26	12.699%	$143.4207	$143.42	$143.40	$143.40
Purchase #5	$147.30	12.168%	$165.2235	$165.22	$165.20	$165.20
Purchase #6	$20.29	5.196%	$21.3443	$21.34	$21.35	$21.30
Purchase #7	$168.45	11.422%	$187.6904	$187.69	$187.70	$187.70
7 purchase totals =	$741.63		$825.3288	$825.32	$825.30	$825.20