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 $143.29   6.522%   $152.6354   $152.64   $152.65   $152.60  
  Purchase #2 $227.41   13.567%   $258.2627   $258.26   $258.25   $258.30  
  Purchase #3 $112.47   3.367%   $116.2569   $116.26   $116.25   $116.30  
  Purchase #4 $176.41   5.243%   $185.6592   $185.66   $185.65   $185.70  
  Purchase #5 $239.60   12.621%   $269.8399   $269.84   $269.85   $269.80  
  Purchase #6 $48.77   3.417%   $50.4365   $50.44   $50.45   $50.40  
  Purchase #7 $151.29   6.769%   $161.5308   $161.53   $161.55   $161.50  
  7 purchase totals = $1,099.24       $1,194.6214   $1,194.63   $1,194.65   $1,194.60