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	$87.68	9.256%	$95.7957	$95.80	$95.80	$95.80
Purchase #2	$163.91	13.229%	$185.5937	$185.59	$185.60	$185.60
Purchase #3	$239.70	13.802%	$272.7834	$272.78	$272.80	$272.80
Purchase #4	$195.79	10.788%	$216.9118	$216.91	$216.90	$216.90
Purchase #5	$142.44	6.448%	$151.6245	$151.62	$151.60	$151.60
Purchase #6	$160.58	7.425%	$172.5031	$172.50	$172.50	$172.50
Purchase #7	$59.36	3.775%	$61.6008	$61.60	$61.60	$61.60
7 purchase totals =	$1,049.46		$1,156.8130	$1,156.80	$1,156.80	$1,156.80