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	$236.94	4.339%	$247.2208	$247.22	$247.20	$247.20
Purchase #2	$99.73	11.729%	$111.4273	$111.43	$111.45	$111.40
Purchase #3	$38.53	10.561%	$42.5992	$42.60	$42.60	$42.60
Purchase #4	$75.88	10.312%	$83.7047	$83.70	$83.70	$83.70
Purchase #5	$223.73	13.496%	$253.9246	$253.92	$253.90	$253.90
Purchase #6	$150.47	6.138%	$159.7058	$159.71	$159.70	$159.70
Purchase #7	$146.66	12.274%	$164.661	$164.66	$164.65	$164.70
7 purchase totals =	$971.94		$1,063.2434	$1,063.24	$1,063.20	$1,063.20