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	$116.79	13.229%	$132.2401	$132.24	$132.25	$132.20
Purchase #2	$31.41	3.663%	$32.5605	$32.56	$32.55	$32.60
Purchase #3	$59.30	12.256%	$66.5678	$66.57	$66.55	$66.60
Purchase #4	$126.54	4.595%	$132.3545	$132.35	$132.35	$132.40
Purchase #5	$231.89	12.756%	$261.4699	$261.47	$261.45	$261.50
Purchase #6	$107.47	7.409%	$115.4325	$115.43	$115.45	$115.40
Purchase #7	$12.54	6.212%	$13.319	$13.32	$13.30	$13.30
7 purchase totals =	$685.94		$753.9443	$753.94	$753.90	$754.00