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	$37.58	7.651%	$40.4552	$40.46	$40.45	$40.50
Purchase #2	$9.31	13.532%	$10.5698	$10.57	$10.55	$10.60
Purchase #3	$204.59	8.169%	$221.303	$221.30	$221.30	$221.30
Purchase #4	$219.31	5.263%	$230.8523	$230.85	$230.85	$230.90
Purchase #5	$16.82	4.590%	$17.592	$17.59	$17.60	$17.60
Purchase #6	$59.69	12.577%	$67.1972	$67.20	$67.20	$67.20
Purchase #7	$59.40	13.570%	$67.4606	$67.46	$67.45	$67.50
7 purchase totals =	$606.70		$655.4301	$655.43	$655.40	$655.60