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 $198.45   8.212%   $214.7467   $214.75   $214.75   $214.70  
  Purchase #2 $118.81   7.425%   $127.6316   $127.63   $127.65   $127.60  
  Purchase #3 $36.40   4.394%   $37.9994   $38.00   $38.00   $38.00  
  Purchase #4 $232.54   11.176%   $258.5287   $258.53   $258.55   $258.50  
  Purchase #5 $52.36   4.510%   $54.7214   $54.72   $54.70   $54.70  
  Purchase #6 $195.62   7.326%   $209.9511   $209.95   $209.95   $210.00  
  Purchase #7 $45.33   6.788%   $48.407   $48.41   $48.40   $48.40  
  7 purchase totals = $879.51       $951.9859   $951.99   $952.00   $951.90