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	$247.73	5.103%	$260.3717	$260.37	$260.35	$260.40
Purchase #2	$105.46	10.731%	$116.7769	$116.78	$116.80	$116.80
Purchase #3	$158.79	3.793%	$164.8129	$164.81	$164.80	$164.80
Purchase #4	$140.78	7.333%	$151.1034	$151.10	$151.10	$151.10
Purchase #5	$186.38	7.226%	$199.8478	$199.85	$199.85	$199.80
Purchase #6	$147.38	8.584%	$160.0311	$160.03	$160.05	$160.00
Purchase #7	$149.56	12.733%	$168.6035	$168.60	$168.60	$168.60
7 purchase totals =	$1,136.08		$1,221.5473	$1,221.54	$1,221.55	$1,221.50