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 $71.81   3.465%   $74.2982   $74.30   $74.30   $74.30  
  Purchase #2 $250.27   4.431%   $261.3595   $261.36   $261.35   $261.40  
  Purchase #3 $202.49   13.190%   $229.1984   $229.20   $229.20   $229.20  
  Purchase #4 $201.38   6.737%   $214.947   $214.95   $214.95   $214.90  
  Purchase #5 $68.61   4.863%   $71.9465   $71.95   $71.95   $71.90  
  Purchase #6 $10.99   10.130%   $12.1033   $12.10   $12.10   $12.10  
  Purchase #7 $139.87   11.505%   $155.962   $155.96   $155.95   $156.00  
  7 purchase totals = $945.42       $1,019.8149   $1,019.82   $1,019.80   $1,019.80