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	$59.85	4.228%	$62.3805	$62.38	$62.40	$62.40
Purchase #2	$111.89	12.150%	$125.4846	$125.48	$125.50	$125.50
Purchase #3	$235.55	10.803%	$260.9965	$261.00	$261.00	$261.00
Purchase #4	$217.34	12.561%	$244.6401	$244.64	$244.65	$244.60
Purchase #5	$136.92	10.370%	$151.1186	$151.12	$151.10	$151.10
Purchase #6	$126.50	10.397%	$139.6522	$139.65	$139.65	$139.70
Purchase #7	$45.47	10.321%	$50.163	$50.16	$50.15	$50.20
7 purchase totals =	$933.52		$1,034.4355	$1,034.43	$1,034.45	$1,034.50