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 $194.96   5.564%   $205.8076   $205.81   $205.80   $205.80  
  Purchase #2 $208.42   6.382%   $221.7214   $221.72   $221.70   $221.70  
  Purchase #3 $50.73   11.105%   $56.3636   $56.36   $56.35   $56.40  
  Purchase #4 $23.54   6.470%   $25.063   $25.06   $25.05   $25.10  
  Purchase #5 $226.96   6.135%   $240.884   $240.88   $240.90   $240.90  
  Purchase #6 $19.95   4.233%   $20.7945   $20.79   $20.80   $20.80  
  Purchase #7 $225.50   10.483%   $249.1392   $249.14   $249.15   $249.10  
  7 purchase totals = $950.06       $1,019.7733   $1,019.76   $1,019.75   $1,019.80