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 $168.65   8.523%   $183.024   $183.02   $183.00   $183.00  
  Purchase #2 $114.79   3.844%   $119.2025   $119.20   $119.20   $119.20  
  Purchase #3 $47.28   13.725%   $53.7692   $53.77   $53.75   $53.80  
  Purchase #4 $210.87   6.647%   $224.8865   $224.89   $224.90   $224.90  
  Purchase #5 $75.79   6.399%   $80.6398   $80.64   $80.65   $80.60  
  Purchase #6 $33.88   5.369%   $35.699   $35.70   $35.70   $35.70  
  Purchase #7 $153.86   13.105%   $174.0234   $174.02   $174.00   $174.00  
  7 purchase totals = $805.12       $871.2444   $871.24   $871.20   $871.20