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	$153.59	12.530%	$172.8348	$172.83	$172.85	$172.80
Purchase #2	$144.72	8.541%	$157.0805	$157.08	$157.10	$157.10
Purchase #3	$7.72	10.680%	$8.5445	$8.54	$8.55	$8.50
Purchase #4	$134.50	6.868%	$143.7375	$143.74	$143.75	$143.70
Purchase #5	$198.48	8.839%	$216.0236	$216.02	$216.00	$216.00
Purchase #6	$112.97	9.391%	$123.579	$123.58	$123.60	$123.60
Purchase #7	$68.61	7.760%	$73.9341	$73.93	$73.95	$73.90
7 purchase totals =	$820.59		$895.7340	$895.72	$895.80	$895.60