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 $48.67   4.705%   $50.9599   $50.96   $50.95   $51.00  
  Purchase #2 $135.68   9.266%   $148.2521   $148.25   $148.25   $148.30  
  Purchase #3 $196.38   5.441%   $207.065   $207.07   $207.05   $207.10  
  Purchase #4 $168.75   11.259%   $187.7496   $187.75   $187.75   $187.70  
  Purchase #5 $202.33   7.815%   $218.1421   $218.14   $218.15   $218.10  
  Purchase #6 $99.91   9.748%   $109.6492   $109.65   $109.65   $109.60  
  Purchase #7 $87.32   6.388%   $92.898   $92.90   $92.90   $92.90  
  7 purchase totals = $939.04       $1,014.7159   $1,014.72   $1,014.70   $1,014.70