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 $69.28   5.777%   $73.2823   $73.28   $73.30   $73.30  
  Purchase #2 $40.44   8.757%   $43.9813   $43.98   $44.00   $44.00  
  Purchase #3 $183.76   13.429%   $208.4371   $208.44   $208.45   $208.40  
  Purchase #4 $113.27   6.245%   $120.3437   $120.34   $120.35   $120.30  
  Purchase #5 $202.30   3.411%   $209.2005   $209.20   $209.20   $209.20  
  Purchase #6 $107.87   7.870%   $116.3594   $116.36   $116.35   $116.40  
  Purchase #7 $67.75   11.158%   $75.3095   $75.31   $75.30   $75.30  
  7 purchase totals = $784.67       $846.9138   $846.91   $846.95   $846.90