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 $241.45   5.723%   $255.2682   $255.27   $255.25   $255.30  
  Purchase #2 $118.77   7.645%   $127.85   $127.85   $127.85   $127.90  
  Purchase #3 $60.25   4.666%   $63.0613   $63.06   $63.05   $63.10  
  Purchase #4 $211.61   12.318%   $237.6761   $237.68   $237.70   $237.70  
  Purchase #5 $129.40   11.487%   $144.2642   $144.26   $144.25   $144.30  
  Purchase #6 $169.54   9.706%   $185.9956   $186.00   $186.00   $186.00  
  Purchase #7 $138.91   5.774%   $146.9307   $146.93   $146.95   $146.90  
  7 purchase totals = $1,069.93       $1,161.0461   $1,161.05   $1,161.05   $1,161.20