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 $240.59   8.470%   $260.968   $260.97   $260.95   $261.00  
  Purchase #2 $81.43   7.146%   $87.249   $87.25   $87.25   $87.20  
  Purchase #3 $115.81   4.187%   $120.659   $120.66   $120.65   $120.70  
  Purchase #4 $19.75   7.332%   $21.1981   $21.20   $21.20   $21.20  
  Purchase #5 $134.69   3.191%   $138.988   $138.99   $139.00   $139.00  
  Purchase #6 $238.36   10.521%   $263.4379   $263.44   $263.45   $263.40  
  Purchase #7 $53.28   6.518%   $56.7528   $56.75   $56.75   $56.80  
  7 purchase totals = $883.91       $949.2528   $949.26   $949.25   $949.30