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 $235.28   11.593%   $262.556   $262.56   $262.55   $262.60  
  Purchase #2 $22.48   11.423%   $25.0479   $25.05   $25.05   $25.00  
  Purchase #3 $86.39   8.294%   $93.5552   $93.56   $93.55   $93.60  
  Purchase #4 $142.67   13.804%   $162.3642   $162.36   $162.35   $162.40  
  Purchase #5 $167.44   11.830%   $187.2482   $187.25   $187.25   $187.20  
  Purchase #6 $160.73   9.193%   $175.5059   $175.51   $175.50   $175.50  
  Purchase #7 $235.33   11.601%   $262.6306   $262.63   $262.65   $262.60  
  7 purchase totals = $1,050.32       $1,168.9080   $1,168.92   $1,168.90   $1,168.90