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	$98.32	3.137%	$101.4043	$101.40	$101.40	$101.40
Purchase #2	$64.42	3.303%	$66.5478	$66.55	$66.55	$66.50
Purchase #3	$34.34	9.136%	$37.4773	$37.48	$37.50	$37.50
Purchase #4	$237.57	4.854%	$249.1016	$249.10	$249.10	$249.10
Purchase #5	$132.94	11.243%	$147.8864	$147.89	$147.90	$147.90
Purchase #6	$214.62	3.762%	$222.694	$222.69	$222.70	$222.70
Purchase #7	$117.56	7.617%	$126.5145	$126.51	$126.50	$126.50
7 purchase totals =	$899.77		$951.6259	$951.62	$951.65	$951.60