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	$86.50	4.590%	$90.4704	$90.47	$90.45	$90.50
Purchase #2	$235.33	12.201%	$264.0426	$264.04	$264.05	$264.00
Purchase #3	$243.26	13.298%	$275.6087	$275.61	$275.60	$275.60
Purchase #4	$154.87	4.695%	$162.1411	$162.14	$162.15	$162.10
Purchase #5	$127.41	13.629%	$144.7747	$144.77	$144.75	$144.80
Purchase #6	$50.94	7.405%	$54.7121	$54.71	$54.70	$54.70
Purchase #7	$87.45	9.196%	$95.4919	$95.49	$95.50	$95.50
7 purchase totals =	$985.76		$1,087.2415	$1,087.23	$1,087.20	$1,087.20