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 $95.85   6.400%   $101.9844   $101.98   $102.00   $102.00  
  Purchase #2 $13.40   8.622%   $14.5553   $14.56   $14.55   $14.60  
  Purchase #3 $248.99   7.508%   $267.6842   $267.68   $267.70   $267.70  
  Purchase #4 $63.25   3.762%   $65.6295   $65.63   $65.65   $65.60  
  Purchase #5 $12.36   10.402%   $13.6457   $13.65   $13.65   $13.60  
  Purchase #6 $225.78   5.257%   $237.6493   $237.65   $237.65   $237.60  
  Purchase #7 $54.69   8.870%   $59.541   $59.54   $59.55   $59.50  
  7 purchase totals = $714.32       $760.6894   $760.69   $760.75   $760.60