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 $183.39   6.860%   $195.9706   $195.97   $195.95   $196.00  
  Purchase #2 $214.38   13.676%   $243.6986   $243.70   $243.70   $243.70  
  Purchase #3 $67.36   8.149%   $72.8492   $72.85   $72.85   $72.80  
  Purchase #4 $133.47   10.732%   $147.794   $147.79   $147.80   $147.80  
  Purchase #5 $47.82   11.219%   $53.1849   $53.18   $53.20   $53.20  
  Purchase #6 $13.64   13.684%   $15.5065   $15.51   $15.50   $15.50  
  Purchase #7 $45.87   4.583%   $47.9722   $47.97   $47.95   $48.00  
  7 purchase totals = $705.93       $776.9760   $776.97   $776.95   $777.00