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 $14.87   12.618%   $16.7463   $16.75   $16.75   $16.70  
  Purchase #2 $207.26   4.844%   $217.2997   $217.30   $217.30   $217.30  
  Purchase #3 $212.86   10.504%   $235.2188   $235.22   $235.20   $235.20  
  Purchase #4 $57.60   7.874%   $62.1354   $62.14   $62.15   $62.10  
  Purchase #5 $240.58   6.522%   $256.2706   $256.27   $256.25   $256.30  
  Purchase #6 $5.90   5.671%   $6.2346   $6.23   $6.25   $6.20  
  Purchase #7 $184.85   8.812%   $201.139   $201.14   $201.15   $201.10  
  7 purchase totals = $923.92       $995.0444   $995.05   $995.05   $994.90