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 $71.61   7.430%   $76.9306   $76.93   $76.95   $76.90  
  Purchase #2 $205.99   4.598%   $215.4614   $215.46   $215.45   $215.50  
  Purchase #3 $249.33   12.426%   $280.3117   $280.31   $280.30   $280.30  
  Purchase #4 $166.64   4.312%   $173.8255   $173.83   $173.85   $173.80  
  Purchase #5 $107.89   9.788%   $118.4503   $118.45   $118.45   $118.50  
  Purchase #6 $95.87   10.797%   $106.2211   $106.22   $106.20   $106.20  
  Purchase #7 $192.63   4.682%   $201.6489   $201.65   $201.65   $201.60  
  7 purchase totals = $1,089.96       $1,172.8495   $1,172.85   $1,172.85   $1,172.80