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 $214.50   10.151%   $236.2739   $236.27   $236.25   $236.30  
  Purchase #2 $97.96   13.692%   $111.3727   $111.37   $111.35   $111.40  
  Purchase #3 $119.59   4.678%   $125.1844   $125.18   $125.20   $125.20  
  Purchase #4 $120.75   11.214%   $134.2909   $134.29   $134.30   $134.30  
  Purchase #5 $184.77   13.677%   $210.041   $210.04   $210.05   $210.00  
  Purchase #6 $190.63   12.815%   $215.0592   $215.06   $215.05   $215.10  
  Purchase #7 $24.97   4.812%   $26.1716   $26.17   $26.15   $26.20  
  7 purchase totals = $953.17       $1,058.3937   $1,058.38   $1,058.35   $1,058.50