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 $113.57   10.689%   $125.7095   $125.71   $125.70   $125.70  
  Purchase #2 $90.80   5.423%   $95.7241   $95.72   $95.70   $95.70  
  Purchase #3 $95.47   12.604%   $107.503   $107.50   $107.50   $107.50  
  Purchase #4 $19.39   7.102%   $20.7671   $20.77   $20.75   $20.80  
  Purchase #5 $173.36   13.855%   $197.379   $197.38   $197.40   $197.40  
  Purchase #6 $191.28   10.849%   $212.032   $212.03   $212.05   $212.00  
  Purchase #7 $20.25   13.379%   $22.9592   $22.96   $22.95   $23.00  
  7 purchase totals = $704.12       $782.0739   $782.07   $782.05   $782.10