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 $213.81   5.141%   $224.802   $224.80   $224.80   $224.80  
  Purchase #2 $34.92   5.709%   $36.9136   $36.91   $36.90   $36.90  
  Purchase #3 $232.77   5.464%   $245.4886   $245.49   $245.50   $245.50  
  Purchase #4 $72.86   7.333%   $78.2028   $78.20   $78.20   $78.20  
  Purchase #5 $236.58   4.469%   $247.1528   $247.15   $247.15   $247.20  
  Purchase #6 $164.90   6.645%   $175.8576   $175.86   $175.85   $175.90  
  Purchase #7 $113.69   10.693%   $125.8469   $125.85   $125.85   $125.80  
  7 purchase totals = $1,069.53       $1,134.2643   $1,134.26   $1,134.25   $1,134.30