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 $77.45   11.357%   $86.246   $86.25   $86.25   $86.20  
  Purchase #2 $114.95   13.635%   $130.6234   $130.62   $130.60   $130.60  
  Purchase #3 $212.59   4.111%   $221.3296   $221.33   $221.35   $221.30  
  Purchase #4 $26.87   10.122%   $29.5898   $29.59   $29.60   $29.60  
  Purchase #5 $64.54   3.389%   $66.7273   $66.73   $66.75   $66.70  
  Purchase #6 $213.66   7.765%   $230.2507   $230.25   $230.25   $230.30  
  Purchase #7 $206.30   11.134%   $229.2694   $229.27   $229.25   $229.30  
  7 purchase totals = $916.36       $994.0362   $994.04   $994.05   $994.00