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 $67.78   12.238%   $76.0749   $76.07   $76.05   $76.10  
  Purchase #2 $154.69   3.660%   $160.3517   $160.35   $160.35   $160.40  
  Purchase #3 $80.82   6.466%   $86.0458   $86.05   $86.05   $86.00  
  Purchase #4 $109.53   6.534%   $116.6867   $116.69   $116.70   $116.70  
  Purchase #5 $230.53   4.246%   $240.3183   $240.32   $240.30   $240.30  
  Purchase #6 $51.69   10.750%   $57.2467   $57.25   $57.25   $57.20  
  Purchase #7 $203.25   5.375%   $214.1747   $214.17   $214.15   $214.20  
  7 purchase totals = $898.29       $950.8988   $950.90   $950.85   $950.90