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	$140.38	5.376%	$147.9268	$147.93	$147.95	$147.90
Purchase #2	$104.82	3.410%	$108.3944	$108.39	$108.40	$108.40
Purchase #3	$176.85	7.659%	$190.3949	$190.39	$190.40	$190.40
Purchase #4	$161.48	5.797%	$170.841	$170.84	$170.85	$170.80
Purchase #5	$50.48	10.652%	$55.8571	$55.86	$55.85	$55.90
Purchase #6	$105.84	4.295%	$110.3858	$110.39	$110.40	$110.40
Purchase #7	$208.94	3.182%	$215.5885	$215.59	$215.60	$215.60
7 purchase totals =	$948.79		$999.3885	$999.39	$999.45	$999.40