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 $84.39   13.158%   $95.494   $95.49   $95.50   $95.50  
  Purchase #2 $101.71   11.435%   $113.3405   $113.34   $113.35   $113.30  
  Purchase #3 $104.87   13.194%   $118.7065   $118.71   $118.70   $118.70  
  Purchase #4 $34.91   8.199%   $37.7723   $37.77   $37.75   $37.80  
  Purchase #5 $86.46   6.431%   $92.0202   $92.02   $92.00   $92.00  
  Purchase #6 $15.45   4.583%   $16.1581   $16.16   $16.15   $16.20  
  Purchase #7 $238.80   9.162%   $260.6789   $260.68   $260.70   $260.70  
  7 purchase totals = $666.59       $734.1705   $734.17   $734.15   $734.20