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 $108.86   4.719%   $113.9971   $114.00   $114.00   $114.00  
  Purchase #2 $107.85   6.780%   $115.1622   $115.16   $115.15   $115.20  
  Purchase #3 $53.42   9.808%   $58.6594   $58.66   $58.65   $58.70  
  Purchase #4 $176.64   8.353%   $191.3947   $191.39   $191.40   $191.40  
  Purchase #5 $159.30   9.857%   $175.0022   $175.00   $175.00   $175.00  
  Purchase #6 $115.98   7.238%   $124.3746   $124.37   $124.35   $124.40  
  Purchase #7 $123.87   11.609%   $138.2501   $138.25   $138.25   $138.30  
  7 purchase totals = $845.92       $916.8403   $916.83   $916.80   $917.00