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	$122.67	4.296%	$127.9399	$127.94	$127.95	$127.90
Purchase #2	$193.99	3.580%	$200.9348	$200.93	$200.95	$200.90
Purchase #3	$132.64	10.694%	$146.8245	$146.82	$146.80	$146.80
Purchase #4	$243.96	12.773%	$275.121	$275.12	$275.10	$275.10
Purchase #5	$111.95	5.244%	$117.8207	$117.82	$117.80	$117.80
Purchase #6	$141.89	9.266%	$155.0375	$155.04	$155.05	$155.00
Purchase #7	$231.57	3.791%	$240.3488	$240.35	$240.35	$240.30
7 purchase totals =	$1,178.67		$1,264.0272	$1,264.02	$1,264.00	$1,263.80