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 $201.67   10.724%   $223.2971   $223.30   $223.30   $223.30  
  Purchase #2 $23.85   10.738%   $26.411   $26.41   $26.40   $26.40  
  Purchase #3 $191.80   7.720%   $206.607   $206.61   $206.60   $206.60  
  Purchase #4 $84.71   4.712%   $88.7015   $88.70   $88.70   $88.70  
  Purchase #5 $221.40   7.858%   $238.7976   $238.80   $238.80   $238.80  
  Purchase #6 $215.59   8.177%   $233.2188   $233.22   $233.20   $233.20  
  Purchase #7 $88.31   8.275%   $95.6177   $95.62   $95.60   $95.60  
  7 purchase totals = $1,027.33       $1,112.6507   $1,112.66   $1,112.60   $1,112.60