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	$41.75	12.107%	$46.8047	$46.80	$46.80	$46.80
Purchase #2	$114.43	9.594%	$125.4084	$125.41	$125.40	$125.40
Purchase #3	$76.51	11.461%	$85.2788	$85.28	$85.30	$85.30
Purchase #4	$93.76	3.473%	$97.0163	$97.02	$97.00	$97.00
Purchase #5	$111.85	10.117%	$123.1659	$123.17	$123.15	$123.20
Purchase #6	$247.43	3.230%	$255.422	$255.42	$255.40	$255.40
Purchase #7	$81.25	13.736%	$92.4105	$92.41	$92.40	$92.40
7 purchase totals =	$766.98		$825.5066	$825.51	$825.45	$825.50