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	$143.77	4.690%	$150.5128	$150.51	$150.50	$150.50
Purchase #2	$18.88	13.672%	$21.4613	$21.46	$21.45	$21.50
Purchase #3	$212.80	4.524%	$222.4271	$222.43	$222.45	$222.40
Purchase #4	$141.48	7.197%	$151.6623	$151.66	$151.65	$151.70
Purchase #5	$164.26	4.769%	$172.0936	$172.09	$172.10	$172.10
Purchase #6	$82.93	6.120%	$88.0053	$88.01	$88.00	$88.00
Purchase #7	$131.31	8.602%	$142.6053	$142.61	$142.60	$142.60
7 purchase totals =	$895.43		$948.7677	$948.77	$948.75	$948.80