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	$200.51	12.569%	$225.7121	$225.71	$225.70	$225.70
Purchase #2	$33.26	11.831%	$37.195	$37.20	$37.20	$37.20
Purchase #3	$73.25	12.562%	$82.4517	$82.45	$82.45	$82.50
Purchase #4	$34.62	11.684%	$38.665	$38.67	$38.65	$38.70
Purchase #5	$132.96	12.848%	$150.0427	$150.04	$150.05	$150.00
Purchase #6	$148.30	13.319%	$168.0521	$168.05	$168.05	$168.10
Purchase #7	$234.76	8.443%	$254.5808	$254.58	$254.60	$254.60
7 purchase totals =	$857.66		$956.6994	$956.70	$956.70	$956.80