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 $184.63   8.137%   $199.6533   $199.65   $199.65   $199.70  
  Purchase #2 $183.61   5.606%   $193.9032   $193.90   $193.90   $193.90  
  Purchase #3 $64.71   8.242%   $70.0434   $70.04   $70.05   $70.00  
  Purchase #4 $210.88   8.189%   $228.149   $228.15   $228.15   $228.10  
  Purchase #5 $185.68   4.446%   $193.9353   $193.94   $193.95   $193.90  
  Purchase #6 $83.97   8.315%   $90.9521   $90.95   $90.95   $91.00  
  Purchase #7 $124.56   7.861%   $134.3517   $134.35   $134.35   $134.40  
  7 purchase totals = $1,038.04       $1,110.9880   $1,110.98   $1,111.00   $1,111.00