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	$101.51	10.143%	$111.8062	$111.81	$111.80	$111.80
Purchase #2	$59.88	3.733%	$62.1153	$62.12	$62.10	$62.10
Purchase #3	$221.79	13.133%	$250.9177	$250.92	$250.90	$250.90
Purchase #4	$242.37	13.265%	$274.5204	$274.52	$274.50	$274.50
Purchase #5	$113.90	3.175%	$117.5163	$117.52	$117.50	$117.50
Purchase #6	$9.85	8.200%	$10.6577	$10.66	$10.65	$10.70
Purchase #7	$204.45	5.145%	$214.969	$214.97	$214.95	$215.00
7 purchase totals =	$953.75		$1,042.5026	$1,042.52	$1,042.40	$1,042.50