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 $94.54   11.710%   $105.6106   $105.61   $105.60   $105.60  
  Purchase #2 $175.99   13.469%   $199.6941   $199.69   $199.70   $199.70  
  Purchase #3 $236.30   13.712%   $268.7015   $268.70   $268.70   $268.70  
  Purchase #4 $191.49   13.505%   $217.3507   $217.35   $217.35   $217.40  
  Purchase #5 $201.93   11.387%   $224.9238   $224.92   $224.90   $224.90  
  Purchase #6 $47.99   3.191%   $49.5214   $49.52   $49.50   $49.50  
  Purchase #7 $155.36   13.105%   $175.7199   $175.72   $175.70   $175.70  
  7 purchase totals = $1,103.60       $1,241.5220   $1,241.51   $1,241.45   $1,241.50