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	$34.94	7.279%	$37.4833	$37.48	$37.50	$37.50
Purchase #2	$239.77	6.610%	$255.6188	$255.62	$255.60	$255.60
Purchase #3	$27.78	12.248%	$31.1825	$31.18	$31.20	$31.20
Purchase #4	$224.62	10.218%	$247.5717	$247.57	$247.55	$247.60
Purchase #5	$241.89	10.160%	$266.466	$266.47	$266.45	$266.50
Purchase #6	$74.85	6.354%	$79.606	$79.61	$79.60	$79.60
Purchase #7	$187.34	9.786%	$205.6731	$205.67	$205.65	$205.70
7 purchase totals =	$1,031.19		$1,123.6014	$1,123.60	$1,123.55	$1,123.70