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	$178.73	3.627%	$185.2125	$185.21	$185.20	$185.20
Purchase #2	$136.84	10.301%	$150.9359	$150.94	$150.95	$150.90
Purchase #3	$89.79	5.849%	$95.0418	$95.04	$95.05	$95.00
Purchase #4	$64.29	6.584%	$68.5229	$68.52	$68.50	$68.50
Purchase #5	$56.45	10.874%	$62.5884	$62.59	$62.60	$62.60
Purchase #6	$246.61	3.761%	$255.885	$255.89	$255.90	$255.90
Purchase #7	$216.39	6.634%	$230.7453	$230.75	$230.75	$230.70
7 purchase totals =	$989.10		$1,048.9318	$1,048.94	$1,048.95	$1,048.80