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 $183.63   7.411%   $197.2388   $197.24   $197.25   $197.20  
  Purchase #2 $175.91   11.817%   $196.6973   $196.70   $196.70   $196.70  
  Purchase #3 $42.62   10.302%   $47.0107   $47.01   $47.00   $47.00  
  Purchase #4 $80.37   6.393%   $85.5081   $85.51   $85.50   $85.50  
  Purchase #5 $175.50   6.228%   $186.4301   $186.43   $186.45   $186.40  
  Purchase #6 $250.79   12.333%   $281.7199   $281.72   $281.70   $281.70  
  Purchase #7 $167.36   13.626%   $190.1645   $190.16   $190.15   $190.20  
  7 purchase totals = $1,076.18       $1,184.7694   $1,184.77   $1,184.75   $1,184.70