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 $248.44   5.349%   $261.7291   $261.73   $261.75   $261.70  
  Purchase #2 $95.81   13.281%   $108.5345   $108.53   $108.55   $108.50  
  Purchase #3 $147.84   4.512%   $154.5105   $154.51   $154.50   $154.50  
  Purchase #4 $181.73   7.175%   $194.7691   $194.77   $194.75   $194.80  
  Purchase #5 $151.62   9.376%   $165.8359   $165.84   $165.85   $165.80  
  Purchase #6 $153.44   5.173%   $161.3775   $161.38   $161.40   $161.40  
  Purchase #7 $65.90   3.873%   $68.4523   $68.45   $68.45   $68.50  
  7 purchase totals = $1,044.78       $1,115.2089   $1,115.21   $1,115.25   $1,115.20