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 $117.33   6.563%   $125.0304   $125.03   $125.05   $125.00  
  Purchase #2 $216.83   7.577%   $233.2592   $233.26   $233.25   $233.30  
  Purchase #3 $27.70   11.644%   $30.9254   $30.93   $30.95   $30.90  
  Purchase #4 $247.55   7.294%   $265.6063   $265.61   $265.60   $265.60  
  Purchase #5 $164.46   11.671%   $183.6541   $183.65   $183.65   $183.70  
  Purchase #6 $155.36   8.491%   $168.5516   $168.55   $168.55   $168.60  
  Purchase #7 $96.38   8.226%   $104.3082   $104.31   $104.30   $104.30  
  7 purchase totals = $1,025.61       $1,111.3352   $1,111.34   $1,111.35   $1,111.40