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 $204.86   10.123%   $225.598   $225.60   $225.60   $225.60  
  Purchase #2 $179.63   8.542%   $194.974   $194.97   $194.95   $195.00  
  Purchase #3 $155.72   3.574%   $161.2854   $161.29   $161.30   $161.30  
  Purchase #4 $126.78   12.652%   $142.8202   $142.82   $142.80   $142.80  
  Purchase #5 $207.71   3.417%   $214.8075   $214.81   $214.80   $214.80  
  Purchase #6 $204.62   13.207%   $231.6442   $231.64   $231.65   $231.60  
  Purchase #7 $127.72   3.105%   $131.6857   $131.69   $131.70   $131.70  
  7 purchase totals = $1,207.04       $1,302.8150   $1,302.82   $1,302.80   $1,302.80