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 $113.26   11.103%   $125.8353   $125.84   $125.85   $125.80  
  Purchase #2 $97.68   10.256%   $107.6981   $107.70   $107.70   $107.70  
  Purchase #3 $93.64   5.692%   $98.97   $98.97   $98.95   $99.00  
  Purchase #4 $101.47   10.730%   $112.3577   $112.36   $112.35   $112.40  
  Purchase #5 $32.34   8.208%   $34.9945   $34.99   $35.00   $35.00  
  Purchase #6 $62.79   13.794%   $71.4513   $71.45   $71.45   $71.50  
  Purchase #7 $46.27   9.665%   $50.742   $50.74   $50.75   $50.70  
  7 purchase totals = $547.45       $602.0489   $602.05   $602.05   $602.10