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	$64.55	4.676%	$67.5684	$67.57	$67.55	$67.60
Purchase #2	$86.27	5.372%	$90.9044	$90.90	$90.90	$90.90
Purchase #3	$118.42	4.304%	$123.5168	$123.52	$123.50	$123.50
Purchase #4	$48.90	11.859%	$54.6991	$54.70	$54.70	$54.70
Purchase #5	$33.59	10.634%	$37.162	$37.16	$37.15	$37.20
Purchase #6	$174.40	8.767%	$189.6896	$189.69	$189.70	$189.70
Purchase #7	$48.78	3.344%	$50.4112	$50.41	$50.40	$50.40
7 purchase totals =	$574.91		$613.9515	$613.95	$613.90	$614.00