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	$85.74	6.659%	$91.4494	$91.45	$91.45	$91.40
Purchase #2	$153.37	13.286%	$173.7467	$173.75	$173.75	$173.70
Purchase #3	$209.85	13.291%	$237.7412	$237.74	$237.75	$237.70
Purchase #4	$63.60	10.282%	$70.1394	$70.14	$70.15	$70.10
Purchase #5	$131.66	9.626%	$144.3336	$144.33	$144.35	$144.30
Purchase #6	$142.91	5.264%	$150.4328	$150.43	$150.45	$150.40
Purchase #7	$99.30	10.379%	$109.6063	$109.61	$109.60	$109.60
7 purchase totals =	$886.43		$977.4494	$977.45	$977.50	$977.20