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 $118.75   5.838%   $125.6826   $125.68   $125.70   $125.70  
  Purchase #2 $10.47   7.192%   $11.223   $11.22   $11.20   $11.20  
  Purchase #3 $105.81   10.286%   $116.6936   $116.69   $116.70   $116.70  
  Purchase #4 $194.49   4.108%   $202.4796   $202.48   $202.50   $202.50  
  Purchase #5 $113.46   10.688%   $125.5866   $125.59   $125.60   $125.60  
  Purchase #6 $156.57   5.346%   $164.9402   $164.94   $164.95   $164.90  
  Purchase #7 $186.78   5.349%   $196.7709   $196.77   $196.75   $196.80  
  7 purchase totals = $886.33       $943.3765   $943.37   $943.40   $943.40