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 $58.34   9.244%   $63.7329   $63.73   $63.75   $63.70  
  Purchase #2 $182.40   10.579%   $201.6961   $201.70   $201.70   $201.70  
  Purchase #3 $105.91   11.437%   $118.0229   $118.02   $118.00   $118.00  
  Purchase #4 $247.26   4.105%   $257.41   $257.41   $257.40   $257.40  
  Purchase #5 $91.56   7.728%   $98.6358   $98.64   $98.65   $98.60  
  Purchase #6 $40.98   4.167%   $42.6876   $42.69   $42.70   $42.70  
  Purchase #7 $154.75   13.234%   $175.2296   $175.23   $175.25   $175.20  
  7 purchase totals = $881.20       $957.4149   $957.42   $957.45   $957.30