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	$57.64	3.684%	$59.7635	$59.76	$59.75	$59.80
Purchase #2	$218.59	9.221%	$238.7462	$238.75	$238.75	$238.70
Purchase #3	$241.25	8.149%	$260.9095	$260.91	$260.90	$260.90
Purchase #4	$48.25	9.588%	$52.8762	$52.88	$52.90	$52.90
Purchase #5	$173.83	9.468%	$190.2882	$190.29	$190.30	$190.30
Purchase #6	$215.51	13.548%	$244.7073	$244.71	$244.70	$244.70
Purchase #7	$21.52	12.676%	$24.2479	$24.25	$24.25	$24.20
7 purchase totals =	$976.59		$1,071.5388	$1,071.55	$1,071.55	$1,071.50