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	$130.78	7.702%	$140.8527	$140.85	$140.85	$140.90
Purchase #2	$111.68	8.584%	$121.2666	$121.27	$121.25	$121.30
Purchase #3	$190.77	4.112%	$198.6145	$198.61	$198.60	$198.60
Purchase #4	$160.39	7.455%	$172.3471	$172.35	$172.35	$172.30
Purchase #5	$112.89	9.503%	$123.6179	$123.62	$123.60	$123.60
Purchase #6	$153.29	10.133%	$168.8229	$168.82	$168.80	$168.80
Purchase #7	$25.65	4.517%	$26.8086	$26.81	$26.80	$26.80
7 purchase totals =	$885.45		$952.3303	$952.33	$952.25	$952.30