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 $62.85   8.782%   $68.3695   $68.37   $68.35   $68.40  
  Purchase #2 $188.51   4.838%   $197.6301   $197.63   $197.65   $197.60  
  Purchase #3 $24.40   5.186%   $25.6654   $25.67   $25.65   $25.70  
  Purchase #4 $205.59   4.294%   $214.418   $214.42   $214.40   $214.40  
  Purchase #5 $241.82   11.402%   $269.3923   $269.39   $269.40   $269.40  
  Purchase #6 $11.42   9.406%   $12.4942   $12.49   $12.50   $12.50  
  Purchase #7 $164.97   6.741%   $176.0906   $176.09   $176.10   $176.10  
  7 purchase totals = $899.56       $964.0601   $964.06   $964.05   $964.10