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 $61.41   11.761%   $68.6324   $68.63   $68.65   $68.60  
  Purchase #2 $233.60   11.746%   $261.0387   $261.04   $261.05   $261.00  
  Purchase #3 $54.33   3.749%   $56.3668   $56.37   $56.35   $56.40  
  Purchase #4 $176.62   6.709%   $188.4694   $188.47   $188.45   $188.50  
  Purchase #5 $225.82   7.548%   $242.8649   $242.86   $242.85   $242.90  
  Purchase #6 $184.85   10.159%   $203.6289   $203.63   $203.65   $203.60  
  Purchase #7 $171.39   13.791%   $195.0264   $195.03   $195.05   $195.00  
  7 purchase totals = $1,108.02       $1,216.0275   $1,216.03   $1,216.05   $1,216.00