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 $116.93   9.257%   $127.7542   $127.75   $127.75   $127.80  
  Purchase #2 $16.71   3.313%   $17.2636   $17.26   $17.25   $17.30  
  Purchase #3 $72.78   5.523%   $76.7996   $76.80   $76.80   $76.80  
  Purchase #4 $182.70   4.312%   $190.578   $190.58   $190.60   $190.60  
  Purchase #5 $61.44   8.610%   $66.73   $66.73   $66.75   $66.70  
  Purchase #6 $29.78   5.149%   $31.3134   $31.31   $31.30   $31.30  
  Purchase #7 $201.72   11.768%   $225.4584   $225.46   $225.45   $225.50  
  7 purchase totals = $682.06       $735.8972   $735.89   $735.90   $736.00