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	$225.50	11.679%	$251.8361	$251.84	$251.85	$251.80
Purchase #2	$157.39	9.503%	$172.3468	$172.35	$172.35	$172.30
Purchase #3	$163.46	9.863%	$179.5821	$179.58	$179.60	$179.60
Purchase #4	$123.38	3.193%	$127.3195	$127.32	$127.30	$127.30
Purchase #5	$97.26	12.874%	$109.7813	$109.78	$109.80	$109.80
Purchase #6	$143.95	6.475%	$153.2708	$153.27	$153.25	$153.30
Purchase #7	$14.82	7.635%	$15.9515	$15.95	$15.95	$16.00
7 purchase totals =	$925.76		$1,010.0881	$1,010.09	$1,010.10	$1,010.10