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 $86.39   11.117%   $95.994   $95.99   $96.00   $96.00  
  Purchase #2 $215.88   13.380%   $244.7647   $244.76   $244.75   $244.80  
  Purchase #3 $199.90   8.635%   $217.1614   $217.16   $217.15   $217.20  
  Purchase #4 $207.36   3.202%   $213.9997   $214.00   $214.00   $214.00  
  Purchase #5 $203.93   8.430%   $221.1213   $221.12   $221.10   $221.10  
  Purchase #6 $115.71   8.277%   $125.2873   $125.29   $125.30   $125.30  
  Purchase #7 $45.73   3.103%   $47.149   $47.15   $47.15   $47.10  
  7 purchase totals = $1,074.90       $1,165.4774   $1,165.47   $1,165.45   $1,165.50