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	$139.80	11.434%	$155.7847	$155.78	$155.80	$155.80
Purchase #2	$76.51	6.351%	$81.3692	$81.37	$81.35	$81.40
Purchase #3	$34.57	7.248%	$37.0756	$37.08	$37.10	$37.10
Purchase #4	$146.83	3.105%	$151.3891	$151.39	$151.40	$151.40
Purchase #5	$180.35	10.315%	$198.9531	$198.95	$198.95	$199.00
Purchase #6	$39.95	5.577%	$42.178	$42.18	$42.20	$42.20
Purchase #7	$59.52	11.741%	$66.5082	$66.51	$66.50	$66.50
7 purchase totals =	$677.53		$733.2579	$733.26	$733.30	$733.40