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	$247.86	13.772%	$281.9953	$282.00	$282.00	$282.00
Purchase #2	$122.57	7.863%	$132.2077	$132.21	$132.20	$132.20
Purchase #3	$77.57	7.788%	$83.6112	$83.61	$83.60	$83.60
Purchase #4	$37.38	10.525%	$41.3142	$41.31	$41.30	$41.30
Purchase #5	$42.58	9.680%	$46.7017	$46.70	$46.70	$46.70
Purchase #6	$82.52	8.408%	$89.4583	$89.46	$89.45	$89.50
Purchase #7	$113.74	10.839%	$126.0683	$126.07	$126.05	$126.10
7 purchase totals =	$724.22		$801.3567	$801.36	$801.30	$801.40