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 $84.58   12.355%   $95.0299   $95.03   $95.05   $95.00  
  Purchase #2 $98.39   3.119%   $101.4588   $101.46   $101.45   $101.50  
  Purchase #3 $57.25   5.824%   $60.5842   $60.58   $60.60   $60.60  
  Purchase #4 $187.67   6.350%   $199.587   $199.59   $199.60   $199.60  
  Purchase #5 $231.94   10.532%   $256.3679   $256.37   $256.35   $256.40  
  Purchase #6 $237.81   8.330%   $257.6196   $257.62   $257.60   $257.60  
  Purchase #7 $25.97   7.790%   $27.9931   $27.99   $28.00   $28.00  
  7 purchase totals = $923.61       $998.6405   $998.64   $998.65   $998.70