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	$176.43	13.627%	$200.4721	$200.47	$200.45	$200.50
Purchase #2	$70.77	7.638%	$76.1754	$76.18	$76.20	$76.20
Purchase #3	$157.91	13.347%	$178.9862	$178.99	$179.00	$179.00
Purchase #4	$54.61	10.753%	$60.4822	$60.48	$60.50	$60.50
Purchase #5	$132.67	13.465%	$150.534	$150.53	$150.55	$150.50
Purchase #6	$123.83	11.103%	$137.5788	$137.58	$137.60	$137.60
Purchase #7	$224.82	9.494%	$246.1644	$246.16	$246.15	$246.20
7 purchase totals =	$941.04		$1,050.3931	$1,050.39	$1,050.45	$1,050.50