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	$227.39	7.371%	$244.1509	$244.15	$244.15	$244.20
Purchase #2	$226.45	5.204%	$238.2345	$238.23	$238.25	$238.20
Purchase #3	$102.37	7.142%	$109.6813	$109.68	$109.70	$109.70
Purchase #4	$160.74	8.137%	$173.8194	$173.82	$173.80	$173.80
Purchase #5	$248.89	13.479%	$282.4379	$282.44	$282.45	$282.40
Purchase #6	$130.71	9.771%	$143.4817	$143.48	$143.50	$143.50
Purchase #7	$55.40	7.186%	$59.381	$59.38	$59.40	$59.40
7 purchase totals =	$1,151.95		$1,251.1867	$1,251.18	$1,251.25	$1,251.20