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 $72.69   5.257%   $76.5113   $76.51   $76.50   $76.50  
  Purchase #2 $203.38   4.429%   $212.3877   $212.39   $212.40   $212.40  
  Purchase #3 $114.87   8.247%   $124.3433   $124.34   $124.35   $124.30  
  Purchase #4 $52.89   10.508%   $58.4477   $58.45   $58.45   $58.40  
  Purchase #5 $88.34   6.702%   $94.2605   $94.26   $94.25   $94.30  
  Purchase #6 $139.71   8.146%   $151.0908   $151.09   $151.10   $151.10  
  Purchase #7 $18.68   7.320%   $20.0474   $20.05   $20.05   $20.00  
  7 purchase totals = $690.56       $737.0887   $737.09   $737.10   $737.00