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 $217.71   5.486%   $229.6536   $229.65   $229.65   $229.70  
  Purchase #2 $248.81   13.275%   $281.8395   $281.84   $281.85   $281.80  
  Purchase #3 $95.72   11.460%   $106.6895   $106.69   $106.70   $106.70  
  Purchase #4 $143.98   5.504%   $151.9047   $151.90   $151.90   $151.90  
  Purchase #5 $194.27   6.275%   $206.4604   $206.46   $206.45   $206.50  
  Purchase #6 $238.44   3.706%   $247.2766   $247.28   $247.30   $247.30  
  Purchase #7 $200.85   12.750%   $226.4584   $226.46   $226.45   $226.50  
  7 purchase totals = $1,339.78       $1,450.2827   $1,450.28   $1,450.30   $1,450.40