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	$237.59	11.764%	$265.5401	$265.54	$265.55	$265.50
Purchase #2	$7.42	3.828%	$7.704	$7.70	$7.70	$7.70
Purchase #3	$66.79	13.756%	$75.9776	$75.98	$76.00	$76.00
Purchase #4	$95.46	4.113%	$99.3863	$99.39	$99.40	$99.40
Purchase #5	$66.58	5.776%	$70.4257	$70.43	$70.45	$70.40
Purchase #6	$163.87	5.203%	$172.3962	$172.40	$172.40	$172.40
Purchase #7	$71.78	6.520%	$76.4601	$76.46	$76.45	$76.50
7 purchase totals =	$709.49		$767.8900	$767.90	$767.95	$767.90