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	$64.52	4.223%	$67.2447	$67.24	$67.25	$67.20
Purchase #2	$29.88	9.353%	$32.6747	$32.67	$32.65	$32.70
Purchase #3	$133.67	7.438%	$143.6124	$143.61	$143.60	$143.60
Purchase #4	$236.82	12.660%	$266.8014	$266.80	$266.80	$266.80
Purchase #5	$33.48	10.515%	$37.0004	$37.00	$37.00	$37.00
Purchase #6	$88.67	13.470%	$100.6138	$100.61	$100.60	$100.60
Purchase #7	$203.65	11.615%	$227.3039	$227.30	$227.30	$227.30
7 purchase totals =	$790.69		$875.2513	$875.23	$875.20	$875.20