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 $214.47   9.499%   $234.8425   $234.84   $234.85   $234.80  
  Purchase #2 $139.76   13.130%   $158.1105   $158.11   $158.10   $158.10  
  Purchase #3 $76.82   11.684%   $85.7956   $85.80   $85.80   $85.80  
  Purchase #4 $62.75   13.757%   $71.3825   $71.38   $71.40   $71.40  
  Purchase #5 $158.63   9.683%   $173.9901   $173.99   $174.00   $174.00  
  Purchase #6 $87.92   5.762%   $92.986   $92.99   $93.00   $93.00  
  Purchase #7 $224.85   3.844%   $233.4932   $233.49   $233.50   $233.50  
  7 purchase totals = $965.20       $1,050.6004   $1,050.60   $1,050.65   $1,050.60