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	$116.40	12.733%	$131.2212	$131.22	$131.20	$131.20
Purchase #2	$52.89	4.261%	$55.1436	$55.14	$55.15	$55.10
Purchase #3	$34.78	5.446%	$36.6741	$36.67	$36.65	$36.70
Purchase #4	$183.35	13.509%	$208.1188	$208.12	$208.10	$208.10
Purchase #5	$144.44	12.286%	$162.1859	$162.19	$162.20	$162.20
Purchase #6	$88.94	12.861%	$100.3786	$100.38	$100.40	$100.40
Purchase #7	$41.61	9.511%	$45.5675	$45.57	$45.55	$45.60
7 purchase totals =	$662.41		$739.2897	$739.29	$739.25	$739.30