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 $219.80   11.557%   $245.2023   $245.20   $245.20   $245.20  
  Purchase #2 $98.97   3.770%   $102.7012   $102.70   $102.70   $102.70  
  Purchase #3 $162.55   5.797%   $171.973   $171.97   $171.95   $172.00  
  Purchase #4 $101.54   13.136%   $114.8783   $114.88   $114.90   $114.90  
  Purchase #5 $152.35   6.669%   $162.5102   $162.51   $162.50   $162.50  
  Purchase #6 $198.89   8.121%   $215.0419   $215.04   $215.05   $215.00  
  Purchase #7 $209.98   7.236%   $225.1742   $225.17   $225.15   $225.20  
  7 purchase totals = $1,144.08       $1,237.4811   $1,237.47   $1,237.45   $1,237.50