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	$243.51	11.400%	$271.2701	$271.27	$271.25	$271.30
Purchase #2	$29.35	13.465%	$33.302	$33.30	$33.30	$33.30
Purchase #3	$117.71	12.644%	$132.5933	$132.59	$132.60	$132.60
Purchase #4	$241.84	13.430%	$274.3191	$274.32	$274.30	$274.30
Purchase #5	$180.70	5.338%	$190.3458	$190.35	$190.35	$190.30
Purchase #6	$80.98	5.603%	$85.5173	$85.52	$85.50	$85.50
Purchase #7	$65.95	3.327%	$68.1442	$68.14	$68.15	$68.10
7 purchase totals =	$960.04		$1,055.4918	$1,055.49	$1,055.45	$1,055.40