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	$56.61	5.422%	$59.6794	$59.68	$59.70	$59.70
Purchase #2	$21.51	6.825%	$22.9781	$22.98	$23.00	$23.00
Purchase #3	$95.56	10.128%	$105.2383	$105.24	$105.25	$105.20
Purchase #4	$81.45	6.633%	$86.8526	$86.85	$86.85	$86.90
Purchase #5	$243.34	12.203%	$273.0348	$273.03	$273.05	$273.00
Purchase #6	$177.53	3.111%	$183.053	$183.05	$183.05	$183.10
Purchase #7	$35.60	6.439%	$37.8923	$37.89	$37.90	$37.90
7 purchase totals =	$711.60		$768.7285	$768.72	$768.80	$768.80