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 $67.45   13.383%   $76.4768   $76.48   $76.50   $76.50  
  Purchase #2 $212.44   3.239%   $219.3209   $219.32   $219.30   $219.30  
  Purchase #3 $223.49   10.461%   $246.8693   $246.87   $246.85   $246.90  
  Purchase #4 $223.37   6.174%   $237.1609   $237.16   $237.15   $237.20  
  Purchase #5 $207.27   12.619%   $233.4254   $233.43   $233.45   $233.40  
  Purchase #6 $128.95   3.131%   $132.9874   $132.99   $133.00   $133.00  
  Purchase #7 $185.62   11.655%   $207.254   $207.25   $207.25   $207.30  
  7 purchase totals = $1,248.59       $1,353.4947   $1,353.50   $1,353.50   $1,353.60