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 $22.36   7.116%   $23.9511   $23.95   $23.95   $24.00  
  Purchase #2 $213.77   5.371%   $225.2516   $225.25   $225.25   $225.30  
  Purchase #3 $131.82   7.687%   $141.953   $141.95   $141.95   $142.00  
  Purchase #4 $116.94   7.361%   $125.548   $125.55   $125.55   $125.50  
  Purchase #5 $17.70   6.623%   $18.8723   $18.87   $18.85   $18.90  
  Purchase #6 $215.30   7.729%   $231.9405   $231.94   $231.95   $231.90  
  Purchase #7 $185.35   7.443%   $199.1456   $199.15   $199.15   $199.10  
  7 purchase totals = $903.24       $966.6621   $966.66   $966.65   $966.70