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	$205.76	9.609%	$225.5315	$225.53	$225.55	$225.50
Purchase #2	$74.72	4.341%	$77.9636	$77.96	$77.95	$78.00
Purchase #3	$23.67	10.762%	$26.2174	$26.22	$26.20	$26.20
Purchase #4	$36.35	6.144%	$38.5833	$38.58	$38.60	$38.60
Purchase #5	$37.90	13.168%	$42.8907	$42.89	$42.90	$42.90
Purchase #6	$37.81	8.618%	$41.0685	$41.07	$41.05	$41.10
Purchase #7	$18.73	3.257%	$19.34	$19.34	$19.35	$19.30
7 purchase totals =	$434.94		$471.5950	$471.59	$471.60	$471.60