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 $84.68   12.543%   $95.3014   $95.30   $95.30   $95.30  
  Purchase #2 $157.84   10.354%   $174.1828   $174.18   $174.20   $174.20  
  Purchase #3 $118.88   9.499%   $130.1724   $130.17   $130.15   $130.20  
  Purchase #4 $147.62   12.295%   $165.7699   $165.77   $165.75   $165.80  
  Purchase #5 $240.57   11.692%   $268.6974   $268.70   $268.70   $268.70  
  Purchase #6 $80.81   5.103%   $84.9337   $84.93   $84.95   $84.90  
  Purchase #7 $52.59   9.103%   $57.3773   $57.38   $57.40   $57.40  
  7 purchase totals = $882.99       $976.4349   $976.43   $976.45   $976.50