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 $196.55   3.564%   $203.555   $203.56   $203.55   $203.60  
  Purchase #2 $214.87   10.272%   $236.9414   $236.94   $236.95   $236.90  
  Purchase #3 $119.50   3.280%   $123.4196   $123.42   $123.40   $123.40  
  Purchase #4 $217.44   3.704%   $225.494   $225.49   $225.50   $225.50  
  Purchase #5 $248.26   7.384%   $266.5915   $266.59   $266.60   $266.60  
  Purchase #6 $184.72   7.262%   $198.1344   $198.13   $198.15   $198.10  
  Purchase #7 $83.58   13.856%   $95.1608   $95.16   $95.15   $95.20  
  7 purchase totals = $1,264.92       $1,349.2967   $1,349.29   $1,349.30   $1,349.30