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 $60.48   3.102%   $62.3561   $62.36   $62.35   $62.40  
  Purchase #2 $107.33   6.577%   $114.3891   $114.39   $114.40   $114.40  
  Purchase #3 $144.95   5.215%   $152.5091   $152.51   $152.50   $152.50  
  Purchase #4 $111.36   4.170%   $116.0037   $116.00   $116.00   $116.00  
  Purchase #5 $24.64   6.525%   $26.2478   $26.25   $26.25   $26.20  
  Purchase #6 $40.87   3.520%   $42.3086   $42.31   $42.30   $42.30  
  Purchase #7 $216.99   3.165%   $223.8577   $223.86   $223.85   $223.90  
  7 purchase totals = $706.62       $737.6721   $737.68   $737.65   $737.70