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 $46.26   3.710%   $47.9762   $47.98   $48.00   $48.00  
  Purchase #2 $209.38   3.127%   $215.9273   $215.93   $215.95   $215.90  
  Purchase #3 $194.71   3.214%   $200.968   $200.97   $200.95   $201.00  
  Purchase #4 $182.60   5.108%   $191.9272   $191.93   $191.95   $191.90  
  Purchase #5 $17.38   11.699%   $19.4133   $19.41   $19.40   $19.40  
  Purchase #6 $66.30   9.465%   $72.5753   $72.58   $72.60   $72.60  
  Purchase #7 $80.54   9.303%   $88.0326   $88.03   $88.05   $88.00  
  7 purchase totals = $797.17       $836.8199   $836.83   $836.90   $836.80