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 $90.42   5.283%   $95.1969   $95.20   $95.20   $95.20  
  Purchase #2 $183.48   7.552%   $197.3364   $197.34   $197.35   $197.30  
  Purchase #3 $240.83   6.706%   $256.9801   $256.98   $257.00   $257.00  
  Purchase #4 $215.87   7.872%   $232.8633   $232.86   $232.85   $232.90  
  Purchase #5 $176.59   4.620%   $184.7485   $184.75   $184.75   $184.70  
  Purchase #6 $193.28   7.229%   $207.2522   $207.25   $207.25   $207.30  
  Purchase #7 $231.96   8.438%   $251.5328   $251.53   $251.55   $251.50  
  7 purchase totals = $1,332.43       $1,425.9102   $1,425.91   $1,425.95   $1,425.90