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 $61.30   9.295%   $66.9978   $67.00   $67.00   $67.00  
  Purchase #2 $103.26   9.386%   $112.952   $112.95   $112.95   $113.00  
  Purchase #3 $217.77   13.866%   $247.966   $247.97   $247.95   $248.00  
  Purchase #4 $153.33   9.432%   $167.7921   $167.79   $167.80   $167.80  
  Purchase #5 $233.88   3.652%   $242.4213   $242.42   $242.40   $242.40  
  Purchase #6 $227.82   6.445%   $242.503   $242.50   $242.50   $242.50  
  Purchase #7 $234.51   13.692%   $266.6191   $266.62   $266.60   $266.60  
  7 purchase totals = $1,231.87       $1,347.2513   $1,347.25   $1,347.20   $1,347.30