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	$121.56	9.266%	$132.8237	$132.82	$132.80	$132.80
Purchase #2	$72.57	13.827%	$82.6043	$82.60	$82.60	$82.60
Purchase #3	$165.34	4.727%	$173.1556	$173.16	$173.15	$173.20
Purchase #4	$175.62	10.364%	$193.8213	$193.82	$193.80	$193.80
Purchase #5	$59.25	13.377%	$67.1759	$67.18	$67.20	$67.20
Purchase #6	$111.94	6.719%	$119.4612	$119.46	$119.45	$119.50
Purchase #7	$95.90	7.694%	$103.2785	$103.28	$103.30	$103.30
7 purchase totals =	$802.18		$872.3205	$872.32	$872.30	$872.40