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	$106.47	7.444%	$114.3956	$114.40	$114.40	$114.40
Purchase #2	$112.66	5.125%	$118.4338	$118.43	$118.45	$118.40
Purchase #3	$36.98	5.452%	$38.9961	$39.00	$39.00	$39.00
Purchase #4	$234.25	11.139%	$260.3431	$260.34	$260.35	$260.30
Purchase #5	$161.67	6.254%	$171.7808	$171.78	$171.80	$171.80
Purchase #6	$247.83	13.205%	$280.556	$280.56	$280.55	$280.60
Purchase #7	$33.85	11.258%	$37.6608	$37.66	$37.65	$37.70
7 purchase totals =	$933.71		$1,022.1662	$1,022.17	$1,022.20	$1,022.20