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	$227.72	4.460%	$237.8763	$237.88	$237.90	$237.90
Purchase #2	$93.81	7.519%	$100.8636	$100.86	$100.85	$100.90
Purchase #3	$206.47	7.389%	$221.7261	$221.73	$221.75	$221.70
Purchase #4	$99.60	10.186%	$109.7453	$109.75	$109.75	$109.70
Purchase #5	$94.59	11.577%	$105.5407	$105.54	$105.55	$105.50
Purchase #6	$25.31	10.576%	$27.9868	$27.99	$28.00	$28.00
Purchase #7	$114.56	7.594%	$123.2597	$123.26	$123.25	$123.30
7 purchase totals =	$862.06		$926.9985	$927.01	$927.05	$927.00