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 $69.27   10.496%   $76.5406   $76.54   $76.55   $76.50  
  Purchase #2 $194.63   5.161%   $204.6749   $204.67   $204.65   $204.70  
  Purchase #3 $215.41   7.288%   $231.1091   $231.11   $231.10   $231.10  
  Purchase #4 $93.25   5.752%   $98.6137   $98.61   $98.60   $98.60  
  Purchase #5 $61.39   8.438%   $66.5701   $66.57   $66.55   $66.60  
  Purchase #6 $22.57   6.840%   $24.1138   $24.11   $24.10   $24.10  
  Purchase #7 $208.36   3.337%   $215.313   $215.31   $215.30   $215.30  
  7 purchase totals = $864.88       $916.9352   $916.92   $916.85   $916.90