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 $43.30   11.330%   $48.2059   $48.21   $48.20   $48.20  
  Purchase #2 $232.75   13.828%   $264.9347   $264.93   $264.95   $264.90  
  Purchase #3 $61.69   5.452%   $65.0533   $65.05   $65.05   $65.10  
  Purchase #4 $157.57   3.135%   $162.5098   $162.51   $162.50   $162.50  
  Purchase #5 $227.75   10.724%   $252.1739   $252.17   $252.15   $252.20  
  Purchase #6 $26.59   9.427%   $29.0966   $29.10   $29.10   $29.10  
  Purchase #7 $209.62   5.583%   $221.3231   $221.32   $221.30   $221.30  
  7 purchase totals = $959.27       $1,043.2973   $1,043.29   $1,043.25   $1,043.30