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	$43.84	10.350%	$48.3774	$48.38	$48.40	$48.40
Purchase #2	$113.75	8.820%	$123.7828	$123.78	$123.80	$123.80
Purchase #3	$233.40	9.861%	$256.4156	$256.42	$256.40	$256.40
Purchase #4	$108.26	11.136%	$120.3158	$120.32	$120.30	$120.30
Purchase #5	$64.69	3.650%	$67.0512	$67.05	$67.05	$67.10
Purchase #6	$132.68	3.308%	$137.0691	$137.07	$137.05	$137.10
Purchase #7	$43.78	10.401%	$48.3336	$48.33	$48.35	$48.30
7 purchase totals =	$740.40		$801.3455	$801.35	$801.35	$801.40