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	$95.32	7.275%	$102.2545	$102.25	$102.25	$102.30
Purchase #2	$43.95	11.434%	$48.9752	$48.98	$49.00	$49.00
Purchase #3	$153.31	5.263%	$161.3787	$161.38	$161.40	$161.40
Purchase #4	$31.32	13.634%	$35.5902	$35.59	$35.60	$35.60
Purchase #5	$247.50	13.196%	$280.1601	$280.16	$280.15	$280.20
Purchase #6	$81.37	11.387%	$90.6356	$90.64	$90.65	$90.60
Purchase #7	$38.31	9.628%	$41.9985	$42.00	$42.00	$42.00
7 purchase totals =	$691.08		$760.9928	$761.00	$761.05	$761.10