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 $69.86   9.458%   $76.4674   $76.47   $76.45   $76.50  
  Purchase #2 $103.95   9.136%   $113.4469   $113.45   $113.45   $113.40  
  Purchase #3 $217.26   10.443%   $239.9485   $239.95   $239.95   $239.90  
  Purchase #4 $102.28   4.528%   $106.9112   $106.91   $106.90   $106.90  
  Purchase #5 $207.96   9.491%   $227.6975   $227.70   $227.70   $227.70  
  Purchase #6 $192.25   11.596%   $214.5433   $214.54   $214.55   $214.50  
  Purchase #7 $177.58   11.109%   $197.3074   $197.31   $197.30   $197.30  
  7 purchase totals = $1,071.14       $1,176.3222   $1,176.33   $1,176.30   $1,176.20