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 $162.92   7.239%   $174.7138   $174.71   $174.70   $174.70  
  Purchase #2 $223.87   9.192%   $244.4481   $244.45   $244.45   $244.40  
  Purchase #3 $52.90   13.395%   $59.986   $59.99   $60.00   $60.00  
  Purchase #4 $168.77   10.455%   $186.4149   $186.41   $186.40   $186.40  
  Purchase #5 $109.61   8.818%   $119.2754   $119.28   $119.30   $119.30  
  Purchase #6 $217.26   8.131%   $234.9254   $234.93   $234.95   $234.90  
  Purchase #7 $93.65   13.103%   $105.921   $105.92   $105.90   $105.90  
  7 purchase totals = $1,028.98       $1,125.6846   $1,125.69   $1,125.70   $1,125.60