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 $60.80   4.865%   $63.7579   $63.76   $63.75   $63.80  
  Purchase #2 $173.77   7.383%   $186.5994   $186.60   $186.60   $186.60  
  Purchase #3 $13.75   3.540%   $14.2368   $14.24   $14.25   $14.20  
  Purchase #4 $231.96   13.254%   $262.704   $262.70   $262.70   $262.70  
  Purchase #5 $148.51   4.714%   $155.5108   $155.51   $155.50   $155.50  
  Purchase #6 $227.97   4.266%   $237.6952   $237.70   $237.70   $237.70  
  Purchase #7 $128.46   4.227%   $133.89   $133.89   $133.90   $133.90  
  7 purchase totals = $985.22       $1,054.3941   $1,054.40   $1,054.40   $1,054.40