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 $245.76   6.867%   $262.6363   $262.64   $262.65   $262.60  
  Purchase #2 $117.38   7.822%   $126.5615   $126.56   $126.55   $126.60  
  Purchase #3 $26.26   7.440%   $28.2137   $28.21   $28.20   $28.20  
  Purchase #4 $8.49   6.692%   $9.0582   $9.06   $9.05   $9.10  
  Purchase #5 $154.76   3.844%   $160.709   $160.71   $160.70   $160.70  
  Purchase #6 $214.40   13.808%   $244.0044   $244.00   $244.00   $244.00  
  Purchase #7 $192.76   13.425%   $218.638   $218.64   $218.65   $218.60  
  7 purchase totals = $959.81       $1,049.8211   $1,049.82   $1,049.80   $1,049.80