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	$131.89	6.629%	$140.633	$140.63	$140.65	$140.60
Purchase #2	$209.85	8.483%	$227.6516	$227.65	$227.65	$227.70
Purchase #3	$206.64	7.716%	$222.5843	$222.58	$222.60	$222.60
Purchase #4	$86.55	4.808%	$90.7113	$90.71	$90.70	$90.70
Purchase #5	$103.90	9.507%	$113.7778	$113.78	$113.80	$113.80
Purchase #6	$78.79	12.655%	$88.7609	$88.76	$88.75	$88.80
Purchase #7	$29.50	13.497%	$33.4816	$33.48	$33.50	$33.50
7 purchase totals =	$847.12		$917.6005	$917.59	$917.65	$917.70