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 $45.43   9.361%   $49.6827   $49.68   $49.70   $49.70  
  Purchase #2 $112.43   4.669%   $117.6794   $117.68   $117.70   $117.70  
  Purchase #3 $208.54   5.275%   $219.5405   $219.54   $219.55   $219.50  
  Purchase #4 $10.63   7.435%   $11.4203   $11.42   $11.40   $11.40  
  Purchase #5 $56.31   11.370%   $62.7124   $62.71   $62.70   $62.70  
  Purchase #6 $242.47   10.118%   $267.0031   $267.00   $267.00   $267.00  
  Purchase #7 $200.59   7.557%   $215.7486   $215.75   $215.75   $215.70  
  7 purchase totals = $876.40       $943.7870   $943.78   $943.80   $943.70