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 $92.56   3.467%   $95.7691   $95.77   $95.75   $95.80  
  Purchase #2 $116.68   8.606%   $126.7215   $126.72   $126.70   $126.70  
  Purchase #3 $100.60   10.303%   $110.9648   $110.96   $110.95   $111.00  
  Purchase #4 $168.66   4.166%   $175.6864   $175.69   $175.70   $175.70  
  Purchase #5 $92.96   12.635%   $104.7055   $104.71   $104.70   $104.70  
  Purchase #6 $118.32   12.360%   $132.9444   $132.94   $132.95   $132.90  
  Purchase #7 $177.87   6.645%   $189.6895   $189.69   $189.70   $189.70  
  7 purchase totals = $867.65       $936.4812   $936.48   $936.45   $936.50