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	$131.86	11.103%	$146.5004	$146.50	$146.50	$146.50
Purchase #2	$65.35	8.430%	$70.859	$70.86	$70.85	$70.90
Purchase #3	$31.83	12.424%	$35.7846	$35.78	$35.80	$35.80
Purchase #4	$7.58	11.585%	$8.4581	$8.46	$8.45	$8.50
Purchase #5	$41.92	5.467%	$44.2118	$44.21	$44.20	$44.20
Purchase #6	$139.86	7.496%	$150.3439	$150.34	$150.35	$150.30
Purchase #7	$19.33	13.104%	$21.863	$21.86	$21.85	$21.90
7 purchase totals =	$437.73		$478.0208	$478.01	$478.00	$478.10