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	$41.37	9.180%	$45.1678	$45.17	$45.15	$45.20
Purchase #2	$142.25	11.163%	$158.1294	$158.13	$158.15	$158.10
Purchase #3	$103.65	13.367%	$117.5049	$117.50	$117.50	$117.50
Purchase #4	$37.31	9.151%	$40.7242	$40.72	$40.70	$40.70
Purchase #5	$72.58	3.850%	$75.3743	$75.37	$75.35	$75.40
Purchase #6	$137.29	6.309%	$145.9516	$145.95	$145.95	$146.00
Purchase #7	$134.64	13.614%	$152.9699	$152.97	$152.95	$153.00
7 purchase totals =	$669.09		$735.8221	$735.81	$735.75	$735.90