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 $108.47   7.477%   $116.5803   $116.58   $116.60   $116.60  
  Purchase #2 $249.31   3.601%   $258.2877   $258.29   $258.30   $258.30  
  Purchase #3 $126.77   13.321%   $143.657   $143.66   $143.65   $143.70  
  Purchase #4 $46.68   4.360%   $48.7152   $48.72   $48.70   $48.70  
  Purchase #5 $60.70   9.862%   $66.6862   $66.69   $66.70   $66.70  
  Purchase #6 $139.63   8.616%   $151.6605   $151.66   $151.65   $151.70  
  Purchase #7 $214.87   11.856%   $240.345   $240.35   $240.35   $240.30  
  7 purchase totals = $946.43       $1,025.9319   $1,025.95   $1,025.95   $1,026.00