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 $214.77   8.605%   $233.251   $233.25   $233.25   $233.30  
  Purchase #2 $127.74   5.711%   $135.0352   $135.04   $135.05   $135.00  
  Purchase #3 $44.53   11.514%   $49.6572   $49.66   $49.65   $49.70  
  Purchase #4 $175.48   13.813%   $199.7191   $199.72   $199.70   $199.70  
  Purchase #5 $179.33   12.558%   $201.8503   $201.85   $201.85   $201.90  
  Purchase #6 $39.90   11.163%   $44.354   $44.35   $44.35   $44.40  
  Purchase #7 $225.41   12.849%   $254.3729   $254.37   $254.35   $254.40  
  7 purchase totals = $1,007.16       $1,118.2397   $1,118.24   $1,118.20   $1,118.40