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 $25.42   5.307%   $26.769   $26.77   $26.75   $26.80  
  Purchase #2 $206.85   4.112%   $215.3557   $215.36   $215.35   $215.40  
  Purchase #3 $154.86   9.600%   $169.7266   $169.73   $169.75   $169.70  
  Purchase #4 $244.89   8.659%   $266.095   $266.10   $266.10   $266.10  
  Purchase #5 $149.25   6.808%   $159.4109   $159.41   $159.40   $159.40  
  Purchase #6 $158.30   10.564%   $175.0228   $175.02   $175.00   $175.00  
  Purchase #7 $136.34   3.681%   $141.3587   $141.36   $141.35   $141.40  
  7 purchase totals = $1,075.91       $1,153.7387   $1,153.75   $1,153.70   $1,153.80