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 $246.52   6.363%   $262.2061   $262.21   $262.20   $262.20  
  Purchase #2 $149.52   6.468%   $159.191   $159.19   $159.20   $159.20  
  Purchase #3 $61.63   8.291%   $66.7397   $66.74   $66.75   $66.70  
  Purchase #4 $69.94   3.401%   $72.3187   $72.32   $72.30   $72.30  
  Purchase #5 $107.41   5.799%   $113.6387   $113.64   $113.65   $113.60  
  Purchase #6 $195.69   3.195%   $201.9423   $201.94   $201.95   $201.90  
  Purchase #7 $74.29   13.346%   $84.2047   $84.20   $84.20   $84.20  
  7 purchase totals = $905.00       $960.2412   $960.24   $960.25   $960.10