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 $113.94   10.233%   $125.5995   $125.60   $125.60   $125.60  
  Purchase #2 $201.69   6.558%   $214.9168   $214.92   $214.90   $214.90  
  Purchase #3 $58.89   4.278%   $61.4093   $61.41   $61.40   $61.40  
  Purchase #4 $230.75   8.699%   $250.8229   $250.82   $250.80   $250.80  
  Purchase #5 $148.99   5.566%   $157.2828   $157.28   $157.30   $157.30  
  Purchase #6 $242.76   8.405%   $263.164   $263.16   $263.15   $263.20  
  Purchase #7 $183.30   5.241%   $192.9068   $192.91   $192.90   $192.90  
  7 purchase totals = $1,180.32       $1,266.1021   $1,266.10   $1,266.05   $1,266.10