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	$208.43	4.672%	$218.1678	$218.17	$218.15	$218.20
Purchase #2	$38.53	4.281%	$40.1795	$40.18	$40.20	$40.20
Purchase #3	$227.88	12.455%	$256.2625	$256.26	$256.25	$256.30
Purchase #4	$209.94	8.375%	$227.5225	$227.52	$227.50	$227.50
Purchase #5	$45.80	10.113%	$50.4318	$50.43	$50.45	$50.40
Purchase #6	$175.48	5.116%	$184.4576	$184.46	$184.45	$184.50
Purchase #7	$42.75	6.244%	$45.4193	$45.42	$45.40	$45.40
7 purchase totals =	$948.81		$1,022.4410	$1,022.44	$1,022.40	$1,022.50