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	$138.97	13.786%	$158.1284	$158.13	$158.15	$158.10
Purchase #2	$143.93	10.374%	$158.8613	$158.86	$158.85	$158.90
Purchase #3	$169.57	3.809%	$176.0289	$176.03	$176.05	$176.00
Purchase #4	$191.89	6.232%	$203.8486	$203.85	$203.85	$203.80
Purchase #5	$32.79	10.631%	$36.2759	$36.28	$36.30	$36.30
Purchase #6	$206.28	7.866%	$222.506	$222.51	$222.50	$222.50
Purchase #7	$156.47	10.500%	$172.8994	$172.90	$172.90	$172.90
7 purchase totals =	$1,039.90		$1,128.5485	$1,128.56	$1,128.60	$1,128.50