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	$66.29	9.393%	$72.5166	$72.52	$72.50	$72.50
Purchase #2	$25.93	3.172%	$26.7525	$26.75	$26.75	$26.80
Purchase #3	$157.53	7.149%	$168.7918	$168.79	$168.80	$168.80
Purchase #4	$169.57	4.763%	$177.6466	$177.65	$177.65	$177.60
Purchase #5	$231.48	10.383%	$255.5146	$255.51	$255.50	$255.50
Purchase #6	$144.46	5.781%	$152.8112	$152.81	$152.80	$152.80
Purchase #7	$164.41	12.731%	$185.341	$185.34	$185.35	$185.30
7 purchase totals =	$959.67		$1,039.3743	$1,039.37	$1,039.35	$1,039.30