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	$174.47	6.407%	$185.6483	$185.65	$185.65	$185.60
Purchase #2	$64.50	11.823%	$72.1258	$72.13	$72.15	$72.10
Purchase #3	$9.28	13.756%	$10.5566	$10.56	$10.55	$10.60
Purchase #4	$202.61	3.763%	$210.2342	$210.23	$210.25	$210.20
Purchase #5	$134.77	10.306%	$148.6594	$148.66	$148.65	$148.70
Purchase #6	$199.70	12.113%	$223.8897	$223.89	$223.90	$223.90
Purchase #7	$203.67	12.273%	$228.6664	$228.67	$228.65	$228.70
7 purchase totals =	$989.00		$1,079.7804	$1,079.79	$1,079.80	$1,079.80