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 $91.63   11.493%   $102.161   $102.16   $102.15   $102.20  
  Purchase #2 $244.99   9.193%   $267.5119   $267.51   $267.50   $267.50  
  Purchase #3 $248.64   10.533%   $274.8293   $274.83   $274.85   $274.80  
  Purchase #4 $249.94   6.411%   $265.9637   $265.96   $265.95   $266.00  
  Purchase #5 $34.31   11.428%   $38.2309   $38.23   $38.25   $38.20  
  Purchase #6 $197.78   4.105%   $205.8989   $205.90   $205.90   $205.90  
  Purchase #7 $169.51   13.471%   $192.3447   $192.34   $192.35   $192.30  
  7 purchase totals = $1,236.80       $1,346.9404   $1,346.93   $1,346.95   $1,346.90