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	$84.35	13.184%	$95.4707	$95.47	$95.45	$95.50
Purchase #2	$75.94	10.244%	$83.7193	$83.72	$83.70	$83.70
Purchase #3	$41.43	11.550%	$46.2152	$46.22	$46.20	$46.20
Purchase #4	$245.56	13.567%	$278.8751	$278.88	$278.90	$278.90
Purchase #5	$158.29	10.144%	$174.3469	$174.35	$174.35	$174.30
Purchase #6	$144.40	9.776%	$158.5165	$158.52	$158.50	$158.50
Purchase #7	$155.57	9.197%	$169.8778	$169.88	$169.90	$169.90
7 purchase totals =	$905.54		$1,007.0215	$1,007.04	$1,007.00	$1,007.00