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	$143.86	5.315%	$151.5062	$151.51	$151.50	$151.50
Purchase #2	$232.57	12.861%	$262.4808	$262.48	$262.50	$262.50
Purchase #3	$86.49	10.481%	$95.555	$95.56	$95.55	$95.60
Purchase #4	$83.81	11.755%	$93.6619	$93.66	$93.65	$93.70
Purchase #5	$188.30	5.313%	$198.3044	$198.30	$198.30	$198.30
Purchase #6	$131.45	6.462%	$139.9443	$139.94	$139.95	$139.90
Purchase #7	$243.43	12.727%	$274.4113	$274.41	$274.40	$274.40
7 purchase totals =	$1,109.91		$1,215.8639	$1,215.86	$1,215.85	$1,215.90