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 $32.25   11.441%   $35.9397   $35.94   $35.95   $35.90  
  Purchase #2 $226.95   6.847%   $242.4893   $242.49   $242.50   $242.50  
  Purchase #3 $150.85   7.220%   $161.7414   $161.74   $161.75   $161.70  
  Purchase #4 $168.45   13.302%   $190.8572   $190.86   $190.85   $190.90  
  Purchase #5 $98.83   3.467%   $102.2564   $102.26   $102.25   $102.30  
  Purchase #6 $59.25   10.536%   $65.4926   $65.49   $65.50   $65.50  
  Purchase #7 $22.51   7.258%   $24.1438   $24.14   $24.15   $24.10  
  7 purchase totals = $759.09       $822.9204   $822.92   $822.95   $822.90