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 $161.67   13.162%   $182.949   $182.95   $182.95   $182.90  
  Purchase #2 $214.70   4.354%   $224.048   $224.05   $224.05   $224.00  
  Purchase #3 $147.47   4.794%   $154.5397   $154.54   $154.55   $154.50  
  Purchase #4 $114.30   5.259%   $120.311   $120.31   $120.30   $120.30  
  Purchase #5 $129.73   3.540%   $134.3224   $134.32   $134.30   $134.30  
  Purchase #6 $248.86   6.227%   $264.3565   $264.36   $264.35   $264.40  
  Purchase #7 $236.75   13.709%   $269.2061   $269.21   $269.20   $269.20  
  7 purchase totals = $1,253.48       $1,349.7327   $1,349.74   $1,349.70   $1,349.60