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	$143.81	10.393%	$158.7562	$158.76	$158.75	$158.80
Purchase #2	$234.46	4.266%	$244.4621	$244.46	$244.45	$244.50
Purchase #3	$121.44	13.218%	$137.4919	$137.49	$137.50	$137.50
Purchase #4	$219.38	12.686%	$247.2105	$247.21	$247.20	$247.20
Purchase #5	$226.78	6.478%	$241.4708	$241.47	$241.45	$241.50
Purchase #6	$230.89	7.586%	$248.4053	$248.41	$248.40	$248.40
Purchase #7	$161.57	7.442%	$173.594	$173.59	$173.60	$173.60
7 purchase totals =	$1,338.33		$1,451.3908	$1,451.39	$1,451.35	$1,451.50