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	$112.72	11.388%	$125.5566	$125.56	$125.55	$125.60
Purchase #2	$7.44	3.261%	$7.6826	$7.68	$7.70	$7.70
Purchase #3	$66.79	10.172%	$73.5839	$73.58	$73.60	$73.60
Purchase #4	$183.72	8.493%	$199.3233	$199.32	$199.30	$199.30
Purchase #5	$99.49	8.672%	$108.1178	$108.12	$108.10	$108.10
Purchase #6	$38.50	10.848%	$42.6765	$42.68	$42.70	$42.70
Purchase #7	$99.79	5.446%	$105.2246	$105.22	$105.20	$105.20
7 purchase totals =	$608.45		$662.1653	$662.16	$662.15	$662.20