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	$102.95	4.648%	$107.7351	$107.74	$107.75	$107.70
Purchase #2	$141.77	8.261%	$153.4816	$153.48	$153.50	$153.50
Purchase #3	$161.54	12.575%	$181.8537	$181.85	$181.85	$181.90
Purchase #4	$120.26	9.522%	$131.7112	$131.71	$131.70	$131.70
Purchase #5	$10.80	13.313%	$12.2378	$12.24	$12.25	$12.20
Purchase #6	$40.48	13.377%	$45.895	$45.90	$45.90	$45.90
Purchase #7	$208.92	12.434%	$234.8971	$234.90	$234.90	$234.90
7 purchase totals =	$786.72		$867.8115	$867.82	$867.85	$867.80