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	$150.87	3.213%	$155.7175	$155.72	$155.70	$155.70
Purchase #2	$88.51	13.673%	$100.612	$100.61	$100.60	$100.60
Purchase #3	$93.65	11.470%	$104.3917	$104.39	$104.40	$104.40
Purchase #4	$35.47	11.341%	$39.4927	$39.49	$39.50	$39.50
Purchase #5	$223.95	10.274%	$246.9586	$246.96	$246.95	$247.00
Purchase #6	$83.45	5.621%	$88.1407	$88.14	$88.15	$88.10
Purchase #7	$132.50	5.558%	$139.8644	$139.86	$139.85	$139.90
7 purchase totals =	$808.40		$875.1776	$875.17	$875.15	$875.20