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	$116.94	12.745%	$131.844	$131.84	$131.85	$131.80
Purchase #2	$69.27	7.562%	$74.5082	$74.51	$74.50	$74.50
Purchase #3	$90.38	11.690%	$100.9454	$100.95	$100.95	$100.90
Purchase #4	$97.79	10.609%	$108.1645	$108.16	$108.15	$108.20
Purchase #5	$120.82	12.186%	$135.5431	$135.54	$135.55	$135.50
Purchase #6	$81.47	6.407%	$86.6898	$86.69	$86.70	$86.70
Purchase #7	$34.27	11.387%	$38.1723	$38.17	$38.15	$38.20
7 purchase totals =	$610.94		$675.8673	$675.86	$675.85	$675.80