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 $86.65   10.404%   $95.6651   $95.67   $95.65   $95.70  
  Purchase #2 $176.30   10.508%   $194.8256   $194.83   $194.85   $194.80  
  Purchase #3 $61.49   12.459%   $69.151   $69.15   $69.15   $69.20  
  Purchase #4 $105.98   8.535%   $115.0254   $115.03   $115.05   $115.00  
  Purchase #5 $39.39   3.346%   $40.708   $40.71   $40.70   $40.70  
  Purchase #6 $32.92   6.745%   $35.1405   $35.14   $35.15   $35.10  
  Purchase #7 $145.44   13.782%   $165.4845   $165.48   $165.50   $165.50  
  7 purchase totals = $648.17       $716.0001   $716.01   $716.05   $716.00