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 $233.67   8.287%   $253.0342   $253.03   $253.05   $253.00  
  Purchase #2 $175.54   11.495%   $195.7183   $195.72   $195.70   $195.70  
  Purchase #3 $199.43   4.533%   $208.4702   $208.47   $208.45   $208.50  
  Purchase #4 $27.40   4.754%   $28.7026   $28.70   $28.70   $28.70  
  Purchase #5 $231.83   11.290%   $258.0036   $258.00   $258.00   $258.00  
  Purchase #6 $213.36   11.524%   $237.9476   $237.95   $237.95   $237.90  
  Purchase #7 $229.47   11.137%   $255.0261   $255.03   $255.05   $255.00  
  7 purchase totals = $1,310.70       $1,436.9026   $1,436.90   $1,436.90   $1,436.80