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	$176.39	9.126%	$192.4874	$192.49	$192.50	$192.50
Purchase #2	$37.51	13.539%	$42.5885	$42.59	$42.60	$42.60
Purchase #3	$33.39	11.839%	$37.343	$37.34	$37.35	$37.30
Purchase #4	$100.73	9.281%	$110.0788	$110.08	$110.10	$110.10
Purchase #5	$119.97	10.557%	$132.6352	$132.64	$132.65	$132.60
Purchase #6	$160.48	5.334%	$169.04	$169.04	$169.05	$169.00
Purchase #7	$183.43	5.462%	$193.4489	$193.45	$193.45	$193.40
7 purchase totals =	$811.90		$877.6218	$877.63	$877.70	$877.50