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 $59.95   4.355%   $62.5608   $62.56   $62.55   $62.60  
  Purchase #2 $76.77   8.208%   $83.0713   $83.07   $83.05   $83.10  
  Purchase #3 $82.96   9.735%   $91.0362   $91.04   $91.05   $91.00  
  Purchase #4 $75.28   9.537%   $82.4595   $82.46   $82.45   $82.50  
  Purchase #5 $149.81   9.287%   $163.7229   $163.72   $163.70   $163.70  
  Purchase #6 $182.71   6.438%   $194.4729   $194.47   $194.45   $194.50  
  Purchase #7 $98.69   7.213%   $105.8085   $105.81   $105.80   $105.80  
  7 purchase totals = $726.17       $783.1321   $783.13   $783.05   $783.20