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 $151.61   10.636%   $167.7352   $167.74   $167.75   $167.70  
  Purchase #2 $220.68   5.103%   $231.9413   $231.94   $231.95   $231.90  
  Purchase #3 $166.74   4.208%   $173.7564   $173.76   $173.75   $173.80  
  Purchase #4 $227.47   7.432%   $244.3756   $244.38   $244.40   $244.40  
  Purchase #5 $205.26   13.758%   $233.4997   $233.50   $233.50   $233.50  
  Purchase #6 $8.96   13.423%   $10.1627   $10.16   $10.15   $10.20  
  Purchase #7 $114.47   7.865%   $123.4731   $123.47   $123.45   $123.50  
  7 purchase totals = $1,095.19       $1,184.9440   $1,184.95   $1,184.95   $1,185.00