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 $53.41   5.308%   $56.245   $56.25   $56.25   $56.20  
  Purchase #2 $158.49   4.479%   $165.5888   $165.59   $165.60   $165.60  
  Purchase #3 $121.82   6.279%   $129.4691   $129.47   $129.45   $129.50  
  Purchase #4 $118.49   3.572%   $122.7225   $122.72   $122.70   $122.70  
  Purchase #5 $113.36   4.609%   $118.5848   $118.58   $118.60   $118.60  
  Purchase #6 $158.68   13.768%   $180.5271   $180.53   $180.55   $180.50  
  Purchase #7 $248.58   6.616%   $265.0261   $265.03   $265.05   $265.00  
  7 purchase totals = $972.83       $1,038.1634   $1,038.17   $1,038.20   $1,038.10