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 $119.42   5.314%   $125.766   $125.77   $125.75   $125.80  
  Purchase #2 $83.77   10.717%   $92.7476   $92.75   $92.75   $92.70  
  Purchase #3 $136.61   8.237%   $147.8626   $147.86   $147.85   $147.90  
  Purchase #4 $201.77   6.791%   $215.4722   $215.47   $215.45   $215.50  
  Purchase #5 $6.65   11.803%   $7.4349   $7.43   $7.45   $7.40  
  Purchase #6 $195.46   9.105%   $213.2566   $213.26   $213.25   $213.30  
  Purchase #7 $202.79   8.675%   $220.382   $220.38   $220.40   $220.40  
  7 purchase totals = $946.47       $1,022.9219   $1,022.92   $1,022.90   $1,023.00