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 $208.42   8.416%   $225.9606   $225.96   $225.95   $226.00  
  Purchase #2 $22.89   6.791%   $24.4445   $24.44   $24.45   $24.40  
  Purchase #3 $171.61   10.744%   $190.0478   $190.05   $190.05   $190.00  
  Purchase #4 $50.83   11.678%   $56.7659   $56.77   $56.75   $56.80  
  Purchase #5 $196.43   7.648%   $211.453   $211.45   $211.45   $211.50  
  Purchase #6 $250.46   5.869%   $265.1595   $265.16   $265.15   $265.20  
  Purchase #7 $126.73   7.811%   $136.6289   $136.63   $136.65   $136.60  
  7 purchase totals = $1,027.37       $1,110.4602   $1,110.46   $1,110.45   $1,110.50