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 $46.96   12.790%   $52.9662   $52.97   $52.95   $53.00  
  Purchase #2 $232.55   8.806%   $253.0284   $253.03   $253.05   $253.00  
  Purchase #3 $150.44   5.416%   $158.5878   $158.59   $158.60   $158.60  
  Purchase #4 $241.29   8.234%   $261.1578   $261.16   $261.15   $261.20  
  Purchase #5 $222.59   6.548%   $237.1652   $237.17   $237.15   $237.20  
  Purchase #6 $102.44   3.632%   $106.1606   $106.16   $106.15   $106.20  
  Purchase #7 $71.56   12.560%   $80.5479   $80.55   $80.55   $80.50  
  7 purchase totals = $1,067.83       $1,149.6139   $1,149.63   $1,149.60   $1,149.70