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 $94.26   4.245%   $98.2613   $98.26   $98.25   $98.30  
  Purchase #2 $239.60   11.118%   $266.2387   $266.24   $266.25   $266.20  
  Purchase #3 $65.55   6.106%   $69.5525   $69.55   $69.55   $69.60  
  Purchase #4 $127.39   4.800%   $133.5047   $133.50   $133.50   $133.50  
  Purchase #5 $82.58   8.133%   $89.2962   $89.30   $89.30   $89.30  
  Purchase #6 $170.81   9.232%   $186.5792   $186.58   $186.60   $186.60  
  Purchase #7 $120.71   3.867%   $125.3779   $125.38   $125.40   $125.40  
  7 purchase totals = $900.90       $968.8105   $968.81   $968.85   $968.90