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	$139.85	3.231%	$144.3686	$144.37	$144.35	$144.40
Purchase #2	$125.89	5.111%	$132.3242	$132.32	$132.30	$132.30
Purchase #3	$148.96	13.774%	$169.4778	$169.48	$169.50	$169.50
Purchase #4	$134.97	13.114%	$152.67	$152.67	$152.65	$152.70
Purchase #5	$144.47	5.339%	$152.1833	$152.18	$152.20	$152.20
Purchase #6	$122.85	13.622%	$139.5846	$139.58	$139.60	$139.60
Purchase #7	$134.94	11.569%	$150.5512	$150.55	$150.55	$150.60
7 purchase totals =	$951.93		$1,041.1597	$1,041.15	$1,041.15	$1,041.30