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 $192.84   7.681%   $207.652   $207.65   $207.65   $207.70  
  Purchase #2 $98.47   3.206%   $101.6269   $101.63   $101.65   $101.60  
  Purchase #3 $158.27   10.697%   $175.2001   $175.20   $175.20   $175.20  
  Purchase #4 $56.58   11.266%   $62.9543   $62.95   $62.95   $63.00  
  Purchase #5 $145.74   8.197%   $157.6863   $157.69   $157.70   $157.70  
  Purchase #6 $16.72   4.721%   $17.5094   $17.51   $17.50   $17.50  
  Purchase #7 $42.41   5.571%   $44.7727   $44.77   $44.75   $44.80  
  7 purchase totals = $711.03       $767.4017   $767.40   $767.40   $767.50