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 $59.27   3.501%   $61.345   $61.35   $61.35   $61.30  
  Purchase #2 $114.95   9.824%   $126.2427   $126.24   $126.25   $126.20  
  Purchase #3 $162.52   7.452%   $174.631   $174.63   $174.65   $174.60  
  Purchase #4 $119.33   4.517%   $124.7201   $124.72   $124.70   $124.70  
  Purchase #5 $179.85   10.324%   $198.4177   $198.42   $198.40   $198.40  
  Purchase #6 $105.30   11.723%   $117.6443   $117.64   $117.65   $117.60  
  Purchase #7 $22.47   6.840%   $24.0069   $24.01   $24.00   $24.00  
  7 purchase totals = $763.69       $827.0077   $827.01   $827.00   $826.80