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	$246.53	13.119%	$278.8723	$278.87	$278.85	$278.90
Purchase #2	$185.86	13.863%	$211.6258	$211.63	$211.65	$211.60
Purchase #3	$136.91	5.772%	$144.8124	$144.81	$144.80	$144.80
Purchase #4	$164.77	8.869%	$179.3835	$179.38	$179.40	$179.40
Purchase #5	$30.86	3.209%	$31.8503	$31.85	$31.85	$31.90
Purchase #6	$21.97	13.854%	$25.0137	$25.01	$25.00	$25.00
Purchase #7	$215.37	8.394%	$233.4482	$233.45	$233.45	$233.40
7 purchase totals =	$1,002.27		$1,105.0062	$1,105.00	$1,105.00	$1,105.00