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 $56.25   10.381%   $62.0893   $62.09   $62.10   $62.10  
  Purchase #2 $238.28   4.359%   $248.6666   $248.67   $248.65   $248.70  
  Purchase #3 $170.97   13.455%   $193.974   $193.97   $193.95   $194.00  
  Purchase #4 $163.74   8.270%   $177.2813   $177.28   $177.30   $177.30  
  Purchase #5 $21.35   5.654%   $22.5571   $22.56   $22.55   $22.60  
  Purchase #6 $122.90   7.410%   $132.0069   $132.01   $132.00   $132.00  
  Purchase #7 $110.96   7.266%   $119.0224   $119.02   $119.00   $119.00  
  7 purchase totals = $884.45       $955.5976   $955.60   $955.55   $955.70