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 $58.81   3.696%   $60.9836   $60.98   $61.00   $61.00  
  Purchase #2 $250.61   4.361%   $261.5391   $261.54   $261.55   $261.50  
  Purchase #3 $201.76   7.462%   $216.8153   $216.82   $216.80   $216.80  
  Purchase #4 $185.58   8.857%   $202.0168   $202.02   $202.00   $202.00  
  Purchase #5 $159.56   12.304%   $179.1923   $179.19   $179.20   $179.20  
  Purchase #6 $225.55   7.607%   $242.7076   $242.71   $242.70   $242.70  
  Purchase #7 $248.40   8.293%   $268.9998   $269.00   $269.00   $269.00  
  7 purchase totals = $1,330.27       $1,432.2545   $1,432.26   $1,432.25   $1,432.20