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	$73.78	6.725%	$78.7417	$78.74	$78.75	$78.70
Purchase #2	$155.81	4.363%	$162.608	$162.61	$162.60	$162.60
Purchase #3	$87.82	13.176%	$99.3912	$99.39	$99.40	$99.40
Purchase #4	$159.98	10.269%	$176.4083	$176.41	$176.40	$176.40
Purchase #5	$109.94	3.259%	$113.5229	$113.52	$113.50	$113.50
Purchase #6	$93.95	6.383%	$99.9468	$99.95	$99.95	$99.90
Purchase #7	$31.48	4.440%	$32.8777	$32.88	$32.90	$32.90
7 purchase totals =	$712.76		$763.4966	$763.50	$763.50	$763.40