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	$64.83	3.833%	$67.3149	$67.31	$67.30	$67.30
Purchase #2	$38.67	12.431%	$43.4771	$43.48	$43.50	$43.50
Purchase #3	$221.45	11.477%	$246.8658	$246.87	$246.85	$246.90
Purchase #4	$81.58	9.249%	$89.1253	$89.13	$89.15	$89.10
Purchase #5	$159.26	7.668%	$171.4721	$171.47	$171.45	$171.50
Purchase #6	$145.57	4.300%	$151.8295	$151.83	$151.85	$151.80
Purchase #7	$198.91	3.188%	$205.2513	$205.25	$205.25	$205.30
7 purchase totals =	$910.27		$975.3360	$975.34	$975.35	$975.40