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	$239.45	6.379%	$254.7245	$254.72	$254.70	$254.70
Purchase #2	$44.73	13.462%	$50.7516	$50.75	$50.75	$50.80
Purchase #3	$172.35	11.754%	$192.608	$192.61	$192.60	$192.60
Purchase #4	$44.33	4.167%	$46.1772	$46.18	$46.20	$46.20
Purchase #5	$59.74	12.151%	$66.999	$67.00	$67.00	$67.00
Purchase #6	$245.63	12.628%	$276.6482	$276.65	$276.65	$276.60
Purchase #7	$55.81	6.611%	$59.4996	$59.50	$59.50	$59.50
7 purchase totals =	$862.04		$947.4081	$947.41	$947.40	$947.40