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 $67.85   7.688%   $73.0663   $73.07   $73.05   $73.10  
  Purchase #2 $119.66   4.537%   $125.089   $125.09   $125.10   $125.10  
  Purchase #3 $222.34   8.661%   $241.5969   $241.60   $241.60   $241.60  
  Purchase #4 $151.30   5.666%   $159.8727   $159.87   $159.85   $159.90  
  Purchase #5 $163.69   6.136%   $173.734   $173.73   $173.75   $173.70  
  Purchase #6 $154.39   3.807%   $160.2676   $160.27   $160.25   $160.30  
  Purchase #7 $7.50   3.621%   $7.7716   $7.77   $7.75   $7.80  
  7 purchase totals = $886.73       $941.3981   $941.40   $941.35   $941.50