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	$234.25	12.121%	$262.6434	$262.64	$262.65	$262.60
Purchase #2	$75.71	8.827%	$82.3929	$82.39	$82.40	$82.40
Purchase #3	$65.35	11.131%	$72.6241	$72.62	$72.60	$72.60
Purchase #4	$38.72	8.582%	$42.043	$42.04	$42.05	$42.00
Purchase #5	$10.25	11.606%	$11.4396	$11.44	$11.45	$11.40
Purchase #6	$121.45	4.132%	$126.4683	$126.47	$126.45	$126.50
Purchase #7	$195.39	4.193%	$203.5827	$203.58	$203.60	$203.60
7 purchase totals =	$741.12		$801.1940	$801.18	$801.20	$801.10