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 $119.35   4.107%   $124.2517   $124.25   $124.25   $124.30  
  Purchase #2 $205.72   10.639%   $227.6066   $227.61   $227.60   $227.60  
  Purchase #3 $66.27   4.577%   $69.3032   $69.30   $69.30   $69.30  
  Purchase #4 $47.53   7.690%   $51.1851   $51.19   $51.20   $51.20  
  Purchase #5 $234.54   6.415%   $249.5857   $249.59   $249.60   $249.60  
  Purchase #6 $156.49   4.783%   $163.9749   $163.97   $163.95   $164.00  
  Purchase #7 $169.91   3.783%   $176.3377   $176.34   $176.35   $176.30  
  7 purchase totals = $999.81       $1,062.2449   $1,062.25   $1,062.25   $1,062.30