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 $197.89   8.748%   $215.2014   $215.20   $215.20   $215.20  
  Purchase #2 $57.47   6.493%   $61.2015   $61.20   $61.20   $61.20  
  Purchase #3 $65.26   12.228%   $73.24   $73.24   $73.25   $73.20  
  Purchase #4 $66.65   8.720%   $72.4619   $72.46   $72.45   $72.50  
  Purchase #5 $129.58   8.643%   $140.7796   $140.78   $140.80   $140.80  
  Purchase #6 $186.92   3.644%   $193.7314   $193.73   $193.75   $193.70  
  Purchase #7 $239.64   10.838%   $265.6122   $265.61   $265.60   $265.60  
  7 purchase totals = $943.41       $1,022.2280   $1,022.22   $1,022.25   $1,022.20