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 $62.99   4.133%   $65.5934   $65.59   $65.60   $65.60  
  Purchase #2 $200.79   3.855%   $208.5305   $208.53   $208.55   $208.50  
  Purchase #3 $216.67   11.275%   $241.0995   $241.10   $241.10   $241.10  
  Purchase #4 $160.30   9.685%   $175.8251   $175.83   $175.85   $175.80  
  Purchase #5 $187.78   5.358%   $197.8413   $197.84   $197.85   $197.80  
  Purchase #6 $163.51   3.321%   $168.9402   $168.94   $168.95   $168.90  
  Purchase #7 $169.80   9.272%   $185.5439   $185.54   $185.55   $185.50  
  7 purchase totals = $1,161.84       $1,243.3739   $1,243.37   $1,243.45   $1,243.20