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 $24.96   4.305%   $26.0345   $26.03   $26.05   $26.00  
  Purchase #2 $209.80   13.278%   $237.6572   $237.66   $237.65   $237.70  
  Purchase #3 $132.90   4.638%   $139.0639   $139.06   $139.05   $139.10  
  Purchase #4 $89.56   10.825%   $99.2549   $99.25   $99.25   $99.30  
  Purchase #5 $199.81   7.117%   $214.0305   $214.03   $214.05   $214.00  
  Purchase #6 $74.61   8.210%   $80.7355   $80.74   $80.75   $80.70  
  Purchase #7 $242.41   5.711%   $256.254   $256.25   $256.25   $256.30  
  7 purchase totals = $974.05       $1,053.0305   $1,053.02   $1,053.05   $1,053.10