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 $59.64   4.734%   $62.4634   $62.46   $62.45   $62.50  
  Purchase #2 $192.95   12.562%   $217.1884   $217.19   $217.20   $217.20  
  Purchase #3 $119.82   5.271%   $126.1357   $126.14   $126.15   $126.10  
  Purchase #4 $186.96   9.728%   $205.1475   $205.15   $205.15   $205.10  
  Purchase #5 $250.64   6.565%   $267.0945   $267.09   $267.10   $267.10  
  Purchase #6 $154.95   11.854%   $173.3178   $173.32   $173.30   $173.30  
  Purchase #7 $213.67   5.586%   $225.6056   $225.61   $225.60   $225.60  
  7 purchase totals = $1,178.63       $1,276.9529   $1,276.96   $1,276.95   $1,276.90