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 $214.65   5.600%   $226.6704   $226.67   $226.65   $226.70  
  Purchase #2 $84.87   12.560%   $95.5297   $95.53   $95.55   $95.50  
  Purchase #3 $53.83   7.587%   $57.9141   $57.91   $57.90   $57.90  
  Purchase #4 $81.67   5.484%   $86.1488   $86.15   $86.15   $86.10  
  Purchase #5 $158.83   8.736%   $172.7054   $172.71   $172.70   $172.70  
  Purchase #6 $239.65   9.315%   $261.9734   $261.97   $261.95   $262.00  
  Purchase #7 $24.91   8.707%   $27.0789   $27.08   $27.10   $27.10  
  7 purchase totals = $858.41       $928.0207   $928.02   $928.00   $928.00