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	$189.52	5.852%	$200.6107	$200.61	$200.60	$200.60
Purchase #2	$89.72	8.849%	$97.6593	$97.66	$97.65	$97.70
Purchase #3	$210.92	8.120%	$228.0467	$228.05	$228.05	$228.00
Purchase #4	$172.32	7.764%	$185.6989	$185.70	$185.70	$185.70
Purchase #5	$77.56	8.150%	$83.8811	$83.88	$83.90	$83.90
Purchase #6	$197.25	4.184%	$205.5029	$205.50	$205.50	$205.50
Purchase #7	$236.60	5.195%	$248.8914	$248.89	$248.90	$248.90
7 purchase totals =	$1,173.89		$1,250.2910	$1,250.29	$1,250.30	$1,250.30