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	$22.95	9.368%	$25.1	$25.10	$25.10	$25.10
Purchase #2	$37.75	4.250%	$39.3544	$39.35	$39.35	$39.40
Purchase #3	$100.80	10.588%	$111.4727	$111.47	$111.45	$111.50
Purchase #4	$171.79	6.474%	$182.9117	$182.91	$182.90	$182.90
Purchase #5	$32.42	10.568%	$35.8461	$35.85	$35.85	$35.80
Purchase #6	$14.33	9.555%	$15.6992	$15.70	$15.70	$15.70
Purchase #7	$134.59	7.531%	$144.726	$144.73	$144.75	$144.70
7 purchase totals =	$514.63		$555.1101	$555.11	$555.10	$555.10