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 $179.75   12.353%   $201.9545   $201.95   $201.95   $202.00  
  Purchase #2 $169.25   12.763%   $190.8514   $190.85   $190.85   $190.90  
  Purchase #3 $242.86   3.341%   $250.974   $250.97   $250.95   $251.00  
  Purchase #4 $111.62   4.225%   $116.3359   $116.34   $116.35   $116.30  
  Purchase #5 $91.61   7.177%   $98.1848   $98.18   $98.20   $98.20  
  Purchase #6 $62.47   12.624%   $70.3562   $70.36   $70.35   $70.40  
  Purchase #7 $185.73   6.702%   $198.1776   $198.18   $198.20   $198.20  
  7 purchase totals = $1,043.29       $1,126.8344   $1,126.83   $1,126.85   $1,127.00