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	$92.93	13.604%	$105.5722	$105.57	$105.55	$105.60
Purchase #2	$151.30	12.513%	$170.2322	$170.23	$170.25	$170.20
Purchase #3	$55.93	13.338%	$63.3899	$63.39	$63.40	$63.40
Purchase #4	$55.59	11.861%	$62.1835	$62.18	$62.20	$62.20
Purchase #5	$53.68	7.813%	$57.874	$57.87	$57.85	$57.90
Purchase #6	$182.72	9.546%	$200.1625	$200.16	$200.15	$200.20
Purchase #7	$37.49	12.554%	$42.1965	$42.20	$42.20	$42.20
7 purchase totals =	$629.64		$701.6108	$701.60	$701.60	$701.70