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 $241.58   5.431%   $254.7002   $254.70   $254.70   $254.70  
  Purchase #2 $214.57   9.201%   $234.3126   $234.31   $234.30   $234.30  
  Purchase #3 $33.43   5.446%   $35.2506   $35.25   $35.25   $35.30  
  Purchase #4 $104.63   3.175%   $107.952   $107.95   $107.95   $108.00  
  Purchase #5 $114.61   12.105%   $128.4835   $128.48   $128.50   $128.50  
  Purchase #6 $233.54   3.504%   $241.7232   $241.72   $241.70   $241.70  
  Purchase #7 $97.44   11.365%   $108.5141   $108.51   $108.50   $108.50  
  7 purchase totals = $1,039.80       $1,110.9362   $1,110.92   $1,110.90   $1,111.00