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	$126.64	11.703%	$141.4607	$141.46	$141.45	$141.50
Purchase #2	$127.45	13.677%	$144.8813	$144.88	$144.90	$144.90
Purchase #3	$153.49	12.141%	$172.1252	$172.13	$172.15	$172.10
Purchase #4	$116.60	13.290%	$132.0961	$132.10	$132.10	$132.10
Purchase #5	$227.84	7.745%	$245.4862	$245.49	$245.50	$245.50
Purchase #6	$17.54	7.802%	$18.9085	$18.91	$18.90	$18.90
Purchase #7	$180.53	12.153%	$202.4698	$202.47	$202.45	$202.50
7 purchase totals =	$950.09		$1,057.4278	$1,057.44	$1,057.45	$1,057.50