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	$135.38	8.549%	$146.9536	$146.95	$146.95	$147.00
Purchase #2	$84.72	11.319%	$94.3095	$94.31	$94.30	$94.30
Purchase #3	$128.89	11.848%	$144.1609	$144.16	$144.15	$144.20
Purchase #4	$130.53	11.195%	$145.1428	$145.14	$145.15	$145.10
Purchase #5	$142.89	13.135%	$161.6586	$161.66	$161.65	$161.70
Purchase #6	$48.53	13.167%	$54.9199	$54.92	$54.90	$54.90
Purchase #7	$134.38	8.161%	$145.3468	$145.35	$145.35	$145.30
7 purchase totals =	$805.32		$892.4921	$892.49	$892.45	$892.50