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	$127.97	6.503%	$136.2919	$136.29	$136.30	$136.30
Purchase #2	$248.25	13.341%	$281.369	$281.37	$281.35	$281.40
Purchase #3	$100.41	3.583%	$104.0077	$104.01	$104.00	$104.00
Purchase #4	$73.73	11.117%	$81.9266	$81.93	$81.95	$81.90
Purchase #5	$143.59	5.103%	$150.9174	$150.92	$150.90	$150.90
Purchase #6	$145.82	13.394%	$165.3511	$165.35	$165.35	$165.40
Purchase #7	$178.77	9.855%	$196.3878	$196.39	$196.40	$196.40
7 purchase totals =	$1,018.54		$1,116.2515	$1,116.26	$1,116.25	$1,116.30