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 $172.84   13.516%   $196.2011   $196.20   $196.20   $196.20  
  Purchase #2 $70.81   6.800%   $75.6251   $75.63   $75.65   $75.60  
  Purchase #3 $179.55   9.511%   $196.627   $196.63   $196.65   $196.60  
  Purchase #4 $101.68   12.504%   $114.3941   $114.39   $114.40   $114.40  
  Purchase #5 $194.80   3.305%   $201.2381   $201.24   $201.25   $201.20  
  Purchase #6 $34.26   5.779%   $36.2399   $36.24   $36.25   $36.20  
  Purchase #7 $65.77   3.194%   $67.8707   $67.87   $67.85   $67.90  
  7 purchase totals = $819.71       $888.1960   $888.20   $888.25   $888.10