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	$37.25	11.709%	$41.6116	$41.61	$41.60	$41.60
Purchase #2	$161.40	6.249%	$171.4859	$171.49	$171.50	$171.50
Purchase #3	$176.25	5.728%	$186.3456	$186.35	$186.35	$186.30
Purchase #4	$92.38	4.475%	$96.514	$96.51	$96.50	$96.50
Purchase #5	$155.93	10.120%	$171.7101	$171.71	$171.70	$171.70
Purchase #6	$186.46	6.728%	$199.005	$199.01	$199.00	$199.00
Purchase #7	$31.56	12.128%	$35.3876	$35.39	$35.40	$35.40
7 purchase totals =	$841.23		$902.0598	$902.07	$902.05	$902.00