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 $23.86   10.197%   $26.293   $26.29   $26.30   $26.30  
  Purchase #2 $175.87   10.264%   $193.9213   $193.92   $193.90   $193.90  
  Purchase #3 $147.64   9.584%   $161.7898   $161.79   $161.80   $161.80  
  Purchase #4 $211.52   5.236%   $222.5952   $222.60   $222.60   $222.60  
  Purchase #5 $168.50   3.355%   $174.1532   $174.15   $174.15   $174.20  
  Purchase #6 $243.99   8.269%   $264.1655   $264.17   $264.15   $264.20  
  Purchase #7 $14.62   5.831%   $15.4725   $15.47   $15.45   $15.50  
  7 purchase totals = $986.00       $1,058.3905   $1,058.39   $1,058.35   $1,058.50