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	$104.42	6.717%	$111.4339	$111.43	$111.45	$111.40
Purchase #2	$65.92	11.433%	$73.4566	$73.46	$73.45	$73.50
Purchase #3	$159.94	13.162%	$180.9913	$180.99	$181.00	$181.00
Purchase #4	$140.92	6.791%	$150.4899	$150.49	$150.50	$150.50
Purchase #5	$205.71	6.207%	$218.4784	$218.48	$218.50	$218.50
Purchase #6	$33.93	10.463%	$37.4801	$37.48	$37.50	$37.50
Purchase #7	$25.55	13.338%	$28.9579	$28.96	$28.95	$29.00
7 purchase totals =	$736.39		$801.2881	$801.29	$801.35	$801.40