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	$182.56	12.642%	$205.6392	$205.64	$205.65	$205.60
Purchase #2	$78.92	8.375%	$85.5296	$85.53	$85.55	$85.50
Purchase #3	$155.71	3.485%	$161.1365	$161.14	$161.15	$161.10
Purchase #4	$136.38	7.500%	$146.6085	$146.61	$146.60	$146.60
Purchase #5	$49.95	9.498%	$54.6943	$54.69	$54.70	$54.70
Purchase #6	$125.82	3.703%	$130.4791	$130.48	$130.50	$130.50
Purchase #7	$120.73	13.851%	$137.4523	$137.45	$137.45	$137.50
7 purchase totals =	$850.07		$921.5395	$921.54	$921.60	$921.50