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	$40.47	12.851%	$45.6708	$45.67	$45.65	$45.70
Purchase #2	$64.43	12.572%	$72.5301	$72.53	$72.55	$72.50
Purchase #3	$31.29	9.849%	$34.3718	$34.37	$34.35	$34.40
Purchase #4	$180.51	6.750%	$192.6944	$192.69	$192.70	$192.70
Purchase #5	$85.94	4.196%	$89.546	$89.55	$89.55	$89.50
Purchase #6	$56.31	3.664%	$58.3732	$58.37	$58.35	$58.40
Purchase #7	$44.80	8.468%	$48.5937	$48.59	$48.60	$48.60
7 purchase totals =	$503.75		$541.7800	$541.77	$541.75	$541.80