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	$96.89	6.789%	$103.4679	$103.47	$103.45	$103.50
Purchase #2	$13.29	5.493%	$14.02	$14.02	$14.00	$14.00
Purchase #3	$142.89	7.317%	$153.3453	$153.35	$153.35	$153.30
Purchase #4	$136.46	5.594%	$144.0936	$144.09	$144.10	$144.10
Purchase #5	$220.41	5.431%	$232.3805	$232.38	$232.40	$232.40
Purchase #6	$64.93	10.734%	$71.8996	$71.90	$71.90	$71.90
Purchase #7	$224.45	12.143%	$251.705	$251.71	$251.70	$251.70
7 purchase totals =	$899.32		$970.9119	$970.92	$970.90	$970.90