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 $58.96   8.468%   $63.9527   $63.95   $63.95   $64.00  
  Purchase #2 $167.29   4.433%   $174.706   $174.71   $174.70   $174.70  
  Purchase #3 $189.95   10.636%   $210.1531   $210.15   $210.15   $210.20  
  Purchase #4 $163.88   9.629%   $179.66   $179.66   $179.65   $179.70  
  Purchase #5 $89.67   8.600%   $97.3816   $97.38   $97.40   $97.40  
  Purchase #6 $201.99   6.562%   $215.2446   $215.24   $215.25   $215.20  
  Purchase #7 $45.73   12.414%   $51.4069   $51.41   $51.40   $51.40  
  7 purchase totals = $917.47       $992.5049   $992.50   $992.50   $992.60