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 $86.30   11.126%   $95.9017   $95.90   $95.90   $95.90  
  Purchase #2 $23.64   8.290%   $25.5998   $25.60   $25.60   $25.60  
  Purchase #3 $39.25   6.620%   $41.8484   $41.85   $41.85   $41.80  
  Purchase #4 $241.88   11.141%   $268.8279   $268.83   $268.85   $268.80  
  Purchase #5 $228.85   12.198%   $256.7651   $256.77   $256.75   $256.80  
  Purchase #6 $212.45   11.290%   $236.4356   $236.44   $236.45   $236.40  
  Purchase #7 $10.39   7.496%   $11.1688   $11.17   $11.15   $11.20  
  7 purchase totals = $842.76       $936.5473   $936.56   $936.55   $936.50