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	$126.72	13.491%	$143.8158	$143.82	$143.80	$143.80
Purchase #2	$159.33	12.144%	$178.679	$178.68	$178.70	$178.70
Purchase #3	$167.72	4.561%	$175.3697	$175.37	$175.35	$175.40
Purchase #4	$116.68	7.605%	$125.5535	$125.55	$125.55	$125.60
Purchase #5	$232.84	12.733%	$262.4875	$262.49	$262.50	$262.50
Purchase #6	$41.56	3.531%	$43.0275	$43.03	$43.05	$43.00
Purchase #7	$40.85	12.483%	$45.9493	$45.95	$45.95	$45.90
7 purchase totals =	$885.70		$974.8823	$974.89	$974.90	$974.90