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	$146.71	10.828%	$162.5958	$162.60	$162.60	$162.60
Purchase #2	$101.47	9.645%	$111.2568	$111.26	$111.25	$111.30
Purchase #3	$71.34	8.500%	$77.4039	$77.40	$77.40	$77.40
Purchase #4	$139.68	8.189%	$151.1184	$151.12	$151.10	$151.10
Purchase #5	$230.50	10.331%	$254.313	$254.31	$254.30	$254.30
Purchase #6	$155.55	8.689%	$169.0657	$169.07	$169.05	$169.10
Purchase #7	$149.34	6.741%	$159.407	$159.41	$159.40	$159.40
7 purchase totals =	$994.59		$1,085.1606	$1,085.17	$1,085.10	$1,085.20