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 $92.66   3.143%   $95.5723   $95.57   $95.55   $95.60  
  Purchase #2 $118.94   4.831%   $124.686   $124.69   $124.70   $124.70  
  Purchase #3 $160.74   5.166%   $169.0438   $169.04   $169.05   $169.00  
  Purchase #4 $86.87   11.598%   $96.9452   $96.95   $96.95   $96.90  
  Purchase #5 $248.82   11.828%   $278.2504   $278.25   $278.25   $278.30  
  Purchase #6 $112.79   3.290%   $116.5008   $116.50   $116.50   $116.50  
  Purchase #7 $151.25   10.861%   $167.6773   $167.68   $167.70   $167.70  
  7 purchase totals = $972.07       $1,048.6758   $1,048.68   $1,048.70   $1,048.70