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 $41.51   5.854%   $43.94   $43.94   $43.95   $43.90  
  Purchase #2 $214.93   3.613%   $222.6954   $222.70   $222.70   $222.70  
  Purchase #3 $48.62   4.731%   $50.9202   $50.92   $50.90   $50.90  
  Purchase #4 $246.72   7.229%   $264.5554   $264.56   $264.55   $264.60  
  Purchase #5 $212.28   6.457%   $225.9869   $225.99   $226.00   $226.00  
  Purchase #6 $164.38   11.341%   $183.0223   $183.02   $183.00   $183.00  
  Purchase #7 $231.66   12.872%   $261.4793   $261.48   $261.50   $261.50  
  7 purchase totals = $1,160.10       $1,252.5995   $1,252.61   $1,252.60   $1,252.60