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 $14.82   9.493%   $16.2269   $16.23   $16.25   $16.20  
  Purchase #2 $168.54   9.239%   $184.1114   $184.11   $184.10   $184.10  
  Purchase #3 $180.44   11.871%   $201.86   $201.86   $201.85   $201.90  
  Purchase #4 $182.76   13.765%   $207.9169   $207.92   $207.90   $207.90  
  Purchase #5 $221.84   8.434%   $240.55   $240.55   $240.55   $240.60  
  Purchase #6 $191.53   5.165%   $201.4225   $201.42   $201.40   $201.40  
  Purchase #7 $53.44   13.452%   $60.6287   $60.63   $60.65   $60.60  
  7 purchase totals = $1,013.37       $1,112.7164   $1,112.72   $1,112.70   $1,112.70