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 $58.63   5.227%   $61.6946   $61.69   $61.70   $61.70  
  Purchase #2 $76.57   13.125%   $86.6198   $86.62   $86.60   $86.60  
  Purchase #3 $105.95   3.515%   $109.6741   $109.67   $109.65   $109.70  
  Purchase #4 $138.95   10.207%   $153.1326   $153.13   $153.15   $153.10  
  Purchase #5 $58.68   7.486%   $63.0728   $63.07   $63.05   $63.10  
  Purchase #6 $195.89   12.621%   $220.6133   $220.61   $220.60   $220.60  
  Purchase #7 $223.48   5.642%   $236.0887   $236.09   $236.10   $236.10  
  7 purchase totals = $858.15       $930.8959   $930.88   $930.85   $930.90