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 $106.46   6.752%   $113.6482   $113.65   $113.65   $113.60  
  Purchase #2 $179.99   7.394%   $193.2985   $193.30   $193.30   $193.30  
  Purchase #3 $116.52   8.399%   $126.3065   $126.31   $126.30   $126.30  
  Purchase #4 $176.37   9.163%   $192.5308   $192.53   $192.55   $192.50  
  Purchase #5 $132.67   3.661%   $137.527   $137.53   $137.55   $137.50  
  Purchase #6 $117.56   12.794%   $132.6006   $132.60   $132.60   $132.60  
  Purchase #7 $244.64   8.646%   $265.7916   $265.79   $265.80   $265.80  
  7 purchase totals = $1,074.21       $1,161.7032   $1,161.71   $1,161.75   $1,161.60