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	$6.86	11.749%	$7.666	$7.67	$7.65	$7.70
Purchase #2	$35.50	4.114%	$36.9605	$36.96	$36.95	$37.00
Purchase #3	$99.36	12.229%	$111.5107	$111.51	$111.50	$111.50
Purchase #4	$51.64	3.631%	$53.515	$53.52	$53.50	$53.50
Purchase #5	$250.93	12.188%	$281.5133	$281.51	$281.50	$281.50
Purchase #6	$45.47	11.852%	$50.8591	$50.86	$50.85	$50.90
Purchase #7	$80.87	9.408%	$88.4782	$88.48	$88.50	$88.50
7 purchase totals =	$570.63		$630.5028	$630.51	$630.45	$630.60