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 $106.98   11.278%   $119.0452   $119.05   $119.05   $119.00  
  Purchase #2 $23.91   10.124%   $26.3306   $26.33   $26.35   $26.30  
  Purchase #3 $236.74   13.842%   $269.5096   $269.51   $269.50   $269.50  
  Purchase #4 $81.98   12.698%   $92.3898   $92.39   $92.40   $92.40  
  Purchase #5 $239.58   10.852%   $265.5792   $265.58   $265.60   $265.60  
  Purchase #6 $6.81   6.585%   $7.2584   $7.26   $7.25   $7.30  
  Purchase #7 $233.82   11.766%   $261.3313   $261.33   $261.35   $261.30  
  7 purchase totals = $929.82       $1,041.4441   $1,041.45   $1,041.50   $1,041.40