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 $85.76   11.453%   $95.5821   $95.58   $95.60   $95.60  
  Purchase #2 $114.97   10.607%   $127.1649   $127.16   $127.15   $127.20  
  Purchase #3 $115.43   3.678%   $119.6755   $119.68   $119.70   $119.70  
  Purchase #4 $16.63   7.209%   $17.8289   $17.83   $17.85   $17.80  
  Purchase #5 $152.31   5.673%   $160.9505   $160.95   $160.95   $161.00  
  Purchase #6 $246.48   4.872%   $258.4885   $258.49   $258.50   $258.50  
  Purchase #7 $213.90   9.480%   $234.1777   $234.18   $234.20   $234.20  
  7 purchase totals = $945.48       $1,013.8681   $1,013.87   $1,013.95   $1,014.00