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 $44.85   8.383%   $48.6098   $48.61   $48.60   $48.60  
  Purchase #2 $209.82   11.158%   $233.2317   $233.23   $233.25   $233.20  
  Purchase #3 $15.92   9.238%   $17.3907   $17.39   $17.40   $17.40  
  Purchase #4 $8.87   3.383%   $9.1701   $9.17   $9.15   $9.20  
  Purchase #5 $196.92   8.283%   $213.2309   $213.23   $213.25   $213.20  
  Purchase #6 $89.25   11.346%   $99.3763   $99.38   $99.40   $99.40  
  Purchase #7 $125.58   4.596%   $131.3517   $131.35   $131.35   $131.40  
  7 purchase totals = $691.21       $752.3612   $752.36   $752.40   $752.40