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 $196.68   8.614%   $213.622   $213.62   $213.60   $213.60  
  Purchase #2 $197.33   13.334%   $223.642   $223.64   $223.65   $223.60  
  Purchase #3 $199.63   3.763%   $207.1421   $207.14   $207.15   $207.10  
  Purchase #4 $147.86   12.416%   $166.2183   $166.22   $166.20   $166.20  
  Purchase #5 $144.63   13.684%   $164.4212   $164.42   $164.40   $164.40  
  Purchase #6 $235.90   10.725%   $261.2003   $261.20   $261.20   $261.20  
  Purchase #7 $189.75   13.621%   $215.5958   $215.60   $215.60   $215.60  
  7 purchase totals = $1,311.78       $1,451.8417   $1,451.84   $1,451.80   $1,451.70