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 $66.88   13.622%   $75.9904   $75.99   $76.00   $76.00  
  Purchase #2 $62.86   12.123%   $70.4805   $70.48   $70.50   $70.50  
  Purchase #3 $215.30   7.484%   $231.4131   $231.41   $231.40   $231.40  
  Purchase #4 $246.53   7.442%   $264.8768   $264.88   $264.90   $264.90  
  Purchase #5 $158.25   10.694%   $175.1733   $175.17   $175.15   $175.20  
  Purchase #6 $181.71   4.823%   $190.4739   $190.47   $190.45   $190.50  
  Purchase #7 $220.76   5.556%   $233.0254   $233.03   $233.05   $233.00  
  7 purchase totals = $1,152.29       $1,241.4334   $1,241.43   $1,241.45   $1,241.50