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 $71.46   7.662%   $76.9353   $76.94   $76.95   $76.90  
  Purchase #2 $149.83   4.249%   $156.1963   $156.20   $156.20   $156.20  
  Purchase #3 $215.99   11.787%   $241.4487   $241.45   $241.45   $241.40  
  Purchase #4 $167.25   5.224%   $175.9871   $175.99   $176.00   $176.00  
  Purchase #5 $60.68   8.544%   $65.8645   $65.86   $65.85   $65.90  
  Purchase #6 $200.38   7.141%   $214.6891   $214.69   $214.70   $214.70  
  Purchase #7 $224.61   11.444%   $250.3144   $250.31   $250.30   $250.30  
  7 purchase totals = $1,090.20       $1,181.4354   $1,181.44   $1,181.45   $1,181.40