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 $113.86   10.292%   $125.5785   $125.58   $125.60   $125.60  
  Purchase #2 $195.73   11.874%   $218.971   $218.97   $218.95   $219.00  
  Purchase #3 $62.63   8.489%   $67.9467   $67.95   $67.95   $67.90  
  Purchase #4 $92.87   12.686%   $104.6515   $104.65   $104.65   $104.70  
  Purchase #5 $47.72   9.450%   $52.2295   $52.23   $52.25   $52.20  
  Purchase #6 $209.85   11.730%   $234.4654   $234.47   $234.45   $234.50  
  Purchase #7 $116.95   3.150%   $120.6339   $120.63   $120.65   $120.60  
  7 purchase totals = $839.61       $924.4765   $924.48   $924.50   $924.50