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	$39.88	13.716%	$45.3499	$45.35	$45.35	$45.30
Purchase #2	$141.29	3.850%	$146.7297	$146.73	$146.75	$146.70
Purchase #3	$45.87	4.822%	$48.0819	$48.08	$48.10	$48.10
Purchase #4	$33.26	10.778%	$36.8448	$36.84	$36.85	$36.80
Purchase #5	$91.42	13.624%	$103.8751	$103.88	$103.90	$103.90
Purchase #6	$22.62	10.790%	$25.0607	$25.06	$25.05	$25.10
Purchase #7	$69.28	4.175%	$72.1724	$72.17	$72.15	$72.20
7 purchase totals =	$443.62		$478.1145	$478.11	$478.15	$478.10