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	$229.87	3.852%	$238.7246	$238.72	$238.70	$238.70
Purchase #2	$208.78	10.149%	$229.9691	$229.97	$229.95	$230.00
Purchase #3	$182.85	7.468%	$196.5052	$196.51	$196.50	$196.50
Purchase #4	$18.62	13.240%	$21.0853	$21.09	$21.10	$21.10
Purchase #5	$162.52	7.644%	$174.943	$174.94	$174.95	$174.90
Purchase #6	$227.49	12.847%	$256.7156	$256.72	$256.70	$256.70
Purchase #7	$207.70	12.788%	$234.2607	$234.26	$234.25	$234.30
7 purchase totals =	$1,237.83		$1,352.2035	$1,352.21	$1,352.15	$1,352.20