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 $44.46   5.296%   $46.8146   $46.81   $46.80   $46.80  
  Purchase #2 $178.70   3.124%   $184.2826   $184.28   $184.30   $184.30  
  Purchase #3 $248.60   8.486%   $269.6962   $269.70   $269.70   $269.70  
  Purchase #4 $136.96   4.866%   $143.6245   $143.62   $143.60   $143.60  
  Purchase #5 $152.36   10.593%   $168.4995   $168.50   $168.50   $168.50  
  Purchase #6 $45.47   6.464%   $48.4092   $48.41   $48.40   $48.40  
  Purchase #7 $174.98   4.751%   $183.2933   $183.29   $183.30   $183.30  
  7 purchase totals = $981.53       $1,044.6199   $1,044.61   $1,044.60   $1,044.60