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 $101.93   12.523%   $114.6947   $114.69   $114.70   $114.70  
  Purchase #2 $183.44   13.779%   $208.7162   $208.72   $208.70   $208.70  
  Purchase #3 $234.33   6.124%   $248.6804   $248.68   $248.70   $248.70  
  Purchase #4 $166.78   9.362%   $182.3939   $182.39   $182.40   $182.40  
  Purchase #5 $207.47   13.743%   $235.9826   $235.98   $236.00   $236.00  
  Purchase #6 $28.47   4.712%   $29.8115   $29.81   $29.80   $29.80  
  Purchase #7 $97.31   9.139%   $106.2032   $106.20   $106.20   $106.20  
  7 purchase totals = $1,019.73       $1,126.4825   $1,126.47   $1,126.50   $1,126.50