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	$36.35	4.245%	$37.8931	$37.89	$37.90	$37.90
Purchase #2	$141.70	3.129%	$146.1338	$146.13	$146.15	$146.10
Purchase #3	$70.80	11.517%	$78.954	$78.95	$78.95	$79.00
Purchase #4	$55.73	7.357%	$59.8301	$59.83	$59.85	$59.80
Purchase #5	$218.46	10.324%	$241.0138	$241.01	$241.00	$241.00
Purchase #6	$11.40	5.851%	$12.067	$12.07	$12.05	$12.10
Purchase #7	$73.38	4.417%	$76.6212	$76.62	$76.60	$76.60
7 purchase totals =	$607.82		$652.5130	$652.50	$652.50	$652.50