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 $34.35   10.691%   $38.0224   $38.02   $38.00   $38.00  
  Purchase #2 $156.56   12.401%   $175.975   $175.98   $176.00   $176.00  
  Purchase #3 $158.82   4.202%   $165.4936   $165.49   $165.50   $165.50  
  Purchase #4 $214.44   7.435%   $230.3836   $230.38   $230.40   $230.40  
  Purchase #5 $171.32   13.176%   $193.8931   $193.89   $193.90   $193.90  
  Purchase #6 $128.68   4.706%   $134.7357   $134.74   $134.75   $134.70  
  Purchase #7 $106.83   13.724%   $121.4913   $121.49   $121.50   $121.50  
  7 purchase totals = $971.00       $1,059.9947   $1,059.99   $1,060.05   $1,060.00