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	$87.38	13.118%	$98.8425	$98.84	$98.85	$98.80
Purchase #2	$92.25	12.376%	$103.6669	$103.67	$103.65	$103.70
Purchase #3	$22.64	10.197%	$24.9486	$24.95	$24.95	$24.90
Purchase #4	$180.60	3.468%	$186.8632	$186.86	$186.85	$186.90
Purchase #5	$77.34	11.189%	$85.9936	$85.99	$86.00	$86.00
Purchase #6	$83.79	8.433%	$90.856	$90.86	$90.85	$90.90
Purchase #7	$31.77	13.762%	$36.1422	$36.14	$36.15	$36.10
7 purchase totals =	$575.77		$627.3130	$627.31	$627.30	$627.30