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	$139.76	5.861%	$147.9513	$147.95	$147.95	$148.00
Purchase #2	$178.42	6.776%	$190.5097	$190.51	$190.50	$190.50
Purchase #3	$87.42	9.694%	$95.8945	$95.89	$95.90	$95.90
Purchase #4	$73.31	12.679%	$82.605	$82.61	$82.60	$82.60
Purchase #5	$117.30	10.583%	$129.7139	$129.71	$129.70	$129.70
Purchase #6	$85.47	6.406%	$90.9452	$90.95	$90.95	$90.90
Purchase #7	$196.76	4.715%	$206.0372	$206.04	$206.05	$206.00
7 purchase totals =	$878.44		$943.6568	$943.66	$943.65	$943.60