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	$159.71	4.275%	$166.5376	$166.54	$166.55	$166.50
Purchase #2	$151.54	12.400%	$170.331	$170.33	$170.35	$170.30
Purchase #3	$243.37	4.265%	$253.7497	$253.75	$253.75	$253.70
Purchase #4	$33.77	9.680%	$37.0389	$37.04	$37.05	$37.00
Purchase #5	$100.79	10.213%	$111.0837	$111.08	$111.10	$111.10
Purchase #6	$230.93	4.428%	$241.1556	$241.16	$241.15	$241.20
Purchase #7	$227.52	8.661%	$247.2255	$247.23	$247.25	$247.20
7 purchase totals =	$1,147.63		$1,227.1220	$1,227.13	$1,227.20	$1,227.00