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 $168.53   8.122%   $182.218   $182.22   $182.20   $182.20  
  Purchase #2 $214.33   4.143%   $223.2097   $223.21   $223.20   $223.20  
  Purchase #3 $16.43   7.798%   $17.7112   $17.71   $17.70   $17.70  
  Purchase #4 $183.91   9.871%   $202.0638   $202.06   $202.05   $202.10  
  Purchase #5 $210.41   10.605%   $232.724   $232.72   $232.70   $232.70  
  Purchase #6 $125.98   4.765%   $131.9829   $131.98   $132.00   $132.00  
  Purchase #7 $123.69   3.619%   $128.1663   $128.17   $128.15   $128.20  
  7 purchase totals = $1,043.28       $1,118.0759   $1,118.07   $1,118.00   $1,118.10