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 $241.27   8.653%   $262.1471   $262.15   $262.15   $262.10  
  Purchase #2 $245.37   8.180%   $265.4413   $265.44   $265.45   $265.40  
  Purchase #3 $193.78   12.709%   $218.4075   $218.41   $218.40   $218.40  
  Purchase #4 $162.96   9.382%   $178.2489   $178.25   $178.25   $178.20  
  Purchase #5 $180.52   5.186%   $189.8818   $189.88   $189.90   $189.90  
  Purchase #6 $12.63   10.752%   $13.988   $13.99   $14.00   $14.00  
  Purchase #7 $208.39   11.405%   $232.1569   $232.16   $232.15   $232.20  
  7 purchase totals = $1,244.92       $1,360.2715   $1,360.28   $1,360.30   $1,360.20