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 $67.62   13.327%   $76.6317   $76.63   $76.65   $76.60  
  Purchase #2 $145.77   10.252%   $160.7143   $160.71   $160.70   $160.70  
  Purchase #3 $25.36   3.250%   $26.1842   $26.18   $26.20   $26.20  
  Purchase #4 $25.81   5.445%   $27.2154   $27.22   $27.20   $27.20  
  Purchase #5 $236.30   8.316%   $255.9507   $255.95   $255.95   $256.00  
  Purchase #6 $219.63   3.384%   $227.0623   $227.06   $227.05   $227.10  
  Purchase #7 $108.82   3.388%   $112.5068   $112.51   $112.50   $112.50  
  7 purchase totals = $829.31       $886.2654   $886.26   $886.25   $886.30