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	$128.78	9.528%	$141.0502	$141.05	$141.05	$141.10
Purchase #2	$134.59	7.480%	$144.6573	$144.66	$144.65	$144.70
Purchase #3	$34.95	6.308%	$37.1546	$37.15	$37.15	$37.20
Purchase #4	$86.45	10.439%	$95.4745	$95.47	$95.45	$95.50
Purchase #5	$220.47	7.752%	$237.5608	$237.56	$237.55	$237.60
Purchase #6	$55.55	9.412%	$60.7784	$60.78	$60.80	$60.80
Purchase #7	$157.62	10.314%	$173.8769	$173.88	$173.90	$173.90
7 purchase totals =	$818.41		$890.5527	$890.55	$890.55	$890.80