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	$43.39	3.865%	$45.067	$45.07	$45.05	$45.10
Purchase #2	$214.25	5.142%	$225.2667	$225.27	$225.25	$225.30
Purchase #3	$147.40	8.253%	$159.5649	$159.56	$159.55	$159.60
Purchase #4	$132.38	3.843%	$137.4674	$137.47	$137.45	$137.50
Purchase #5	$199.40	10.599%	$220.5344	$220.53	$220.55	$220.50
Purchase #6	$22.43	8.620%	$24.3635	$24.36	$24.35	$24.40
Purchase #7	$190.34	10.143%	$209.6462	$209.65	$209.65	$209.60
7 purchase totals =	$949.59		$1,021.9101	$1,021.91	$1,021.85	$1,022.00