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	$196.55	13.143%	$222.3826	$222.38	$222.40	$222.40
Purchase #2	$94.94	10.160%	$104.5859	$104.59	$104.60	$104.60
Purchase #3	$104.29	7.734%	$112.3558	$112.36	$112.35	$112.40
Purchase #4	$172.88	5.195%	$181.8611	$181.86	$181.85	$181.90
Purchase #5	$7.51	5.566%	$7.928	$7.93	$7.95	$7.90
Purchase #6	$128.36	11.485%	$143.1021	$143.10	$143.10	$143.10
Purchase #7	$23.30	4.264%	$24.2935	$24.29	$24.30	$24.30
7 purchase totals =	$727.83		$796.5090	$796.51	$796.55	$796.60