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 $182.86   10.209%   $201.5282   $201.53   $201.55   $201.50  
  Purchase #2 $112.80   10.548%   $124.6981   $124.70   $124.70   $124.70  
  Purchase #3 $21.84   13.631%   $24.817   $24.82   $24.80   $24.80  
  Purchase #4 $43.64   8.618%   $47.4009   $47.40   $47.40   $47.40  
  Purchase #5 $171.96   6.538%   $183.2027   $183.20   $183.20   $183.20  
  Purchase #6 $181.66   7.550%   $195.3753   $195.38   $195.40   $195.40  
  Purchase #7 $159.75   7.192%   $171.2392   $171.24   $171.25   $171.20  
  7 purchase totals = $874.51       $948.2614   $948.27   $948.30   $948.20