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	$196.47	10.757%	$217.6043	$217.60	$217.60	$217.60
Purchase #2	$120.81	5.773%	$127.7844	$127.78	$127.80	$127.80
Purchase #3	$200.34	13.368%	$227.1215	$227.12	$227.10	$227.10
Purchase #4	$166.77	3.186%	$172.0833	$172.08	$172.10	$172.10
Purchase #5	$157.45	7.498%	$169.2556	$169.26	$169.25	$169.30
Purchase #6	$36.67	11.505%	$40.8889	$40.89	$40.90	$40.90
Purchase #7	$118.97	12.413%	$133.7377	$133.74	$133.75	$133.70
7 purchase totals =	$997.48		$1,088.4757	$1,088.47	$1,088.50	$1,088.50