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 $127.45   13.649%   $144.8457   $144.85   $144.85   $144.80  
  Purchase #2 $207.83   13.863%   $236.6415   $236.64   $236.65   $236.60  
  Purchase #3 $23.85   5.523%   $25.1672   $25.17   $25.15   $25.20  
  Purchase #4 $69.43   3.145%   $71.6136   $71.61   $71.60   $71.60  
  Purchase #5 $158.34   7.249%   $169.8181   $169.82   $169.80   $169.80  
  Purchase #6 $93.93   10.577%   $103.865   $103.87   $103.85   $103.90  
  Purchase #7 $186.57   6.165%   $198.072   $198.07   $198.05   $198.10  
  7 purchase totals = $867.40       $950.0231   $950.03   $949.95   $950.00