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 $60.85   13.652%   $69.1572   $69.16   $69.15   $69.20  
  Purchase #2 $35.67   12.600%   $40.1644   $40.16   $40.15   $40.20  
  Purchase #3 $248.90   5.376%   $262.2809   $262.28   $262.30   $262.30  
  Purchase #4 $91.59   9.486%   $100.2782   $100.28   $100.30   $100.30  
  Purchase #5 $53.39   6.675%   $56.9538   $56.95   $56.95   $57.00  
  Purchase #6 $212.98   6.544%   $226.9174   $226.92   $226.90   $226.90  
  Purchase #7 $102.26   11.328%   $113.844   $113.84   $113.85   $113.80  
  7 purchase totals = $805.64       $869.5959   $869.59   $869.60   $869.70