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 $241.95   10.281%   $266.8249   $266.82   $266.80   $266.80  
  Purchase #2 $226.50   3.830%   $235.175   $235.18   $235.20   $235.20  
  Purchase #3 $32.99   3.665%   $34.1991   $34.20   $34.20   $34.20  
  Purchase #4 $241.73   10.673%   $267.5298   $267.53   $267.55   $267.50  
  Purchase #5 $191.62   5.658%   $202.4619   $202.46   $202.45   $202.50  
  Purchase #6 $75.67   8.679%   $82.2374   $82.24   $82.25   $82.20  
  Purchase #7 $62.48   7.853%   $67.3866   $67.39   $67.40   $67.40  
  7 purchase totals = $1,072.94       $1,155.8147   $1,155.82   $1,155.85   $1,155.80