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 $61.99   4.781%   $64.9537   $64.95   $64.95   $65.00  
  Purchase #2 $177.90   9.712%   $195.1776   $195.18   $195.20   $195.20  
  Purchase #3 $115.60   10.389%   $127.6097   $127.61   $127.60   $127.60  
  Purchase #4 $52.74   6.398%   $56.1143   $56.11   $56.10   $56.10  
  Purchase #5 $230.37   13.297%   $261.0023   $261.00   $261.00   $261.00  
  Purchase #6 $225.65   6.589%   $240.5181   $240.52   $240.50   $240.50  
  Purchase #7 $123.28   8.739%   $134.0534   $134.05   $134.05   $134.10  
  7 purchase totals = $987.53       $1,079.4291   $1,079.42   $1,079.40   $1,079.50