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 $184.66   8.228%   $199.8538   $199.85   $199.85   $199.90  
  Purchase #2 $208.86   3.748%   $216.6881   $216.69   $216.70   $216.70  
  Purchase #3 $140.76   10.524%   $155.5736   $155.57   $155.55   $155.60  
  Purchase #4 $170.33   13.503%   $193.3297   $193.33   $193.35   $193.30  
  Purchase #5 $236.91   7.192%   $253.9486   $253.95   $253.95   $253.90  
  Purchase #6 $159.47   4.419%   $166.517   $166.52   $166.50   $166.50  
  Purchase #7 $14.32   9.760%   $15.7176   $15.72   $15.70   $15.70  
  7 purchase totals = $1,115.31       $1,201.6284   $1,201.63   $1,201.60   $1,201.60