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 $45.62   5.372%   $48.0707   $48.07   $48.05   $48.10  
  Purchase #2 $201.71   6.554%   $214.9301   $214.93   $214.95   $214.90  
  Purchase #3 $198.94   3.730%   $206.3605   $206.36   $206.35   $206.40  
  Purchase #4 $21.88   3.217%   $22.5839   $22.58   $22.60   $22.60  
  Purchase #5 $248.54   8.680%   $270.1133   $270.11   $270.10   $270.10  
  Purchase #6 $241.58   4.591%   $252.6709   $252.67   $252.65   $252.70  
  Purchase #7 $71.56   13.421%   $81.1641   $81.16   $81.15   $81.20  
  7 purchase totals = $1,029.83       $1,095.8935   $1,095.88   $1,095.85   $1,096.00