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	$241.41	4.814%	$253.0315	$253.03	$253.05	$253.00
Purchase #2	$128.56	7.251%	$137.8819	$137.88	$137.90	$137.90
Purchase #3	$199.34	11.148%	$221.5624	$221.56	$221.55	$221.60
Purchase #4	$76.99	8.561%	$83.5811	$83.58	$83.60	$83.60
Purchase #5	$142.94	3.838%	$148.426	$148.43	$148.45	$148.40
Purchase #6	$151.80	6.370%	$161.4697	$161.47	$161.45	$161.50
Purchase #7	$180.63	5.580%	$190.7092	$190.71	$190.70	$190.70
7 purchase totals =	$1,121.67		$1,196.6618	$1,196.66	$1,196.70	$1,196.70