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 $118.54   5.620%   $125.2019   $125.20   $125.20   $125.20  
  Purchase #2 $203.90   6.378%   $216.9047   $216.90   $216.90   $216.90  
  Purchase #3 $192.94   12.605%   $217.2601   $217.26   $217.25   $217.30  
  Purchase #4 $155.81   11.536%   $173.7842   $173.78   $173.80   $173.80  
  Purchase #5 $67.40   13.554%   $76.5354   $76.54   $76.55   $76.50  
  Purchase #6 $19.89   6.203%   $21.1238   $21.12   $21.10   $21.10  
  Purchase #7 $170.95   6.863%   $182.6823   $182.68   $182.70   $182.70  
  7 purchase totals = $929.43       $1,013.4924   $1,013.48   $1,013.50   $1,013.50