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	$39.53	10.130%	$43.5344	$43.53	$43.55	$43.50
Purchase #2	$18.60	10.293%	$20.5145	$20.51	$20.50	$20.50
Purchase #3	$239.43	7.285%	$256.8725	$256.87	$256.85	$256.90
Purchase #4	$163.80	5.207%	$172.3291	$172.33	$172.35	$172.30
Purchase #5	$150.51	3.118%	$155.2029	$155.20	$155.20	$155.20
Purchase #6	$189.31	5.259%	$199.2658	$199.27	$199.25	$199.30
Purchase #7	$13.77	11.131%	$15.3027	$15.30	$15.30	$15.30
7 purchase totals =	$814.95		$863.0219	$863.01	$863.00	$863.00