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 $87.62   9.684%   $96.1051   $96.11   $96.10   $96.10  
  Purchase #2 $224.90   10.718%   $249.0048   $249.00   $249.00   $249.00  
  Purchase #3 $101.78   11.111%   $113.0888   $113.09   $113.10   $113.10  
  Purchase #4 $138.66   7.311%   $148.7974   $148.80   $148.80   $148.80  
  Purchase #5 $34.32   6.318%   $36.4883   $36.49   $36.50   $36.50  
  Purchase #6 $55.67   4.392%   $58.115   $58.12   $58.10   $58.10  
  Purchase #7 $235.48   5.480%   $248.3843   $248.38   $248.40   $248.40  
  7 purchase totals = $878.43       $949.9837   $949.99   $950.00   $950.00