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	$209.29	13.753%	$238.0737	$238.07	$238.05	$238.10
Purchase #2	$61.43	6.184%	$65.2288	$65.23	$65.25	$65.20
Purchase #3	$140.65	7.842%	$151.6798	$151.68	$151.70	$151.70
Purchase #4	$242.49	5.764%	$256.4671	$256.47	$256.45	$256.50
Purchase #5	$148.42	4.578%	$155.2147	$155.21	$155.20	$155.20
Purchase #6	$135.78	4.488%	$141.8738	$141.87	$141.85	$141.90
Purchase #7	$215.42	13.648%	$244.8205	$244.82	$244.80	$244.80
7 purchase totals =	$1,153.48		$1,253.3584	$1,253.35	$1,253.30	$1,253.40