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 $62.32   8.496%   $67.6147   $67.61   $67.60   $67.60  
  Purchase #2 $82.69   11.532%   $92.2258   $92.23   $92.25   $92.20  
  Purchase #3 $188.34   6.871%   $201.2808   $201.28   $201.30   $201.30  
  Purchase #4 $61.77   8.466%   $66.9994   $67.00   $67.00   $67.00  
  Purchase #5 $15.38   10.699%   $17.0255   $17.03   $17.05   $17.00  
  Purchase #6 $124.90   13.377%   $141.6079   $141.61   $141.60   $141.60  
  Purchase #7 $209.68   4.528%   $219.1743   $219.17   $219.15   $219.20  
  7 purchase totals = $745.08       $805.9284   $805.93   $805.95   $805.90