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 $192.46   4.444%   $201.0129   $201.01   $201.00   $201.00  
  Purchase #2 $201.87   13.669%   $229.4636   $229.46   $229.45   $229.50  
  Purchase #3 $234.64   7.256%   $251.6655   $251.67   $251.65   $251.70  
  Purchase #4 $33.93   4.369%   $35.4124   $35.41   $35.40   $35.40  
  Purchase #5 $16.71   9.387%   $18.2786   $18.28   $18.30   $18.30  
  Purchase #6 $17.89   10.427%   $19.7554   $19.76   $19.75   $19.80  
  Purchase #7 $239.43   11.262%   $266.3946   $266.39   $266.40   $266.40  
  7 purchase totals = $936.93       $1,021.9830   $1,021.98   $1,021.95   $1,022.10