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 $141.85   7.614%   $152.6505   $152.65   $152.65   $152.70  
  Purchase #2 $163.61   8.148%   $176.9409   $176.94   $176.95   $176.90  
  Purchase #3 $18.35   8.370%   $19.8859   $19.89   $19.90   $19.90  
  Purchase #4 $108.63   12.557%   $122.2707   $122.27   $122.25   $122.30  
  Purchase #5 $157.50   8.739%   $171.2639   $171.26   $171.25   $171.30  
  Purchase #6 $45.27   9.856%   $49.7318   $49.73   $49.75   $49.70  
  Purchase #7 $67.92   4.157%   $70.7434   $70.74   $70.75   $70.70  
  7 purchase totals = $703.13       $763.4871   $763.48   $763.50   $763.50