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	$40.50	8.108%	$43.7837	$43.78	$43.80	$43.80
Purchase #2	$244.88	8.407%	$265.4671	$265.47	$265.45	$265.50
Purchase #3	$61.84	8.106%	$66.8528	$66.85	$66.85	$66.90
Purchase #4	$48.55	4.484%	$50.727	$50.73	$50.75	$50.70
Purchase #5	$32.71	13.145%	$37.0097	$37.01	$37.00	$37.00
Purchase #6	$36.31	5.717%	$38.3858	$38.39	$38.40	$38.40
Purchase #7	$206.92	11.205%	$230.1054	$230.11	$230.10	$230.10
7 purchase totals =	$671.71		$732.3315	$732.34	$732.35	$732.40