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 $69.25   9.682%   $75.9548   $75.95   $75.95   $76.00  
  Purchase #2 $183.57   12.449%   $206.4226   $206.42   $206.40   $206.40  
  Purchase #3 $54.40   6.575%   $57.9768   $57.98   $58.00   $58.00  
  Purchase #4 $22.81   9.331%   $24.9384   $24.94   $24.95   $24.90  
  Purchase #5 $60.42   8.681%   $65.6651   $65.67   $65.65   $65.70  
  Purchase #6 $202.32   3.809%   $210.0264   $210.03   $210.05   $210.00  
  Purchase #7 $217.89   10.721%   $241.25   $241.25   $241.25   $241.30  
  7 purchase totals = $810.66       $882.2341   $882.24   $882.25   $882.30