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 $57.51   10.703%   $63.6653   $63.67   $63.65   $63.70  
  Purchase #2 $118.56   8.576%   $128.7277   $128.73   $128.75   $128.70  
  Purchase #3 $228.80   4.466%   $239.0182   $239.02   $239.00   $239.00  
  Purchase #4 $103.95   13.553%   $118.0383   $118.04   $118.05   $118.00  
  Purchase #5 $162.90   8.366%   $176.5282   $176.53   $176.55   $176.50  
  Purchase #6 $170.69   12.644%   $192.272   $192.27   $192.25   $192.30  
  Purchase #7 $202.45   11.638%   $226.0111   $226.01   $226.00   $226.00  
  7 purchase totals = $1,044.86       $1,144.2608   $1,144.27   $1,144.25   $1,144.20