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 $222.87   10.140%   $245.469   $245.47   $245.45   $245.50  
  Purchase #2 $60.60   5.169%   $63.7324   $63.73   $63.75   $63.70  
  Purchase #3 $70.29   12.483%   $79.0643   $79.06   $79.05   $79.10  
  Purchase #4 $178.71   12.332%   $200.7485   $200.75   $200.75   $200.70  
  Purchase #5 $93.62   11.236%   $104.1391   $104.14   $104.15   $104.10  
  Purchase #6 $239.61   7.540%   $257.6766   $257.68   $257.70   $257.70  
  Purchase #7 $162.25   10.423%   $179.1613   $179.16   $179.15   $179.20  
  7 purchase totals = $1,027.95       $1,129.9912   $1,129.99   $1,130.00   $1,130.00