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 $62.26   8.624%   $67.6293   $67.63   $67.65   $67.60  
  Purchase #2 $112.60   3.776%   $116.8518   $116.85   $116.85   $116.90  
  Purchase #3 $223.95   9.610%   $245.4716   $245.47   $245.45   $245.50  
  Purchase #4 $47.56   3.452%   $49.2018   $49.20   $49.20   $49.20  
  Purchase #5 $63.67   5.195%   $66.9777   $66.98   $67.00   $67.00  
  Purchase #6 $148.47   8.605%   $161.2458   $161.25   $161.25   $161.20  
  Purchase #7 $220.40   9.126%   $240.5137   $240.51   $240.50   $240.50  
  7 purchase totals = $878.91       $947.8917   $947.89   $947.90   $947.90