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	$201.71	10.397%	$222.6818	$222.68	$222.70	$222.70
Purchase #2	$100.45	13.693%	$114.2046	$114.20	$114.20	$114.20
Purchase #3	$213.78	11.594%	$238.5657	$238.57	$238.55	$238.60
Purchase #4	$139.99	13.161%	$158.4141	$158.41	$158.40	$158.40
Purchase #5	$157.91	4.766%	$165.436	$165.44	$165.45	$165.40
Purchase #6	$28.59	8.420%	$30.9973	$31.00	$31.00	$31.00
Purchase #7	$137.84	5.411%	$145.2985	$145.30	$145.30	$145.30
7 purchase totals =	$980.27		$1,075.5980	$1,075.60	$1,075.60	$1,075.60