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	$139.80	3.442%	$144.6119	$144.61	$144.60	$144.60
Purchase #2	$140.56	5.644%	$148.4932	$148.49	$148.50	$148.50
Purchase #3	$47.40	6.592%	$50.5246	$50.52	$50.50	$50.50
Purchase #4	$113.76	4.366%	$118.7268	$118.73	$118.75	$118.70
Purchase #5	$117.56	8.338%	$127.3622	$127.36	$127.35	$127.40
Purchase #6	$30.57	7.767%	$32.9444	$32.94	$32.95	$32.90
Purchase #7	$95.35	4.638%	$99.7723	$99.77	$99.75	$99.80
7 purchase totals =	$685.00		$722.4354	$722.42	$722.40	$722.40