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 $192.59   8.355%   $208.6809   $208.68   $208.70   $208.70  
  Purchase #2 $66.66   7.440%   $71.6195   $71.62   $71.60   $71.60  
  Purchase #3 $146.83   7.669%   $158.0904   $158.09   $158.10   $158.10  
  Purchase #4 $148.64   4.247%   $154.9527   $154.95   $154.95   $155.00  
  Purchase #5 $166.94   7.149%   $178.8745   $178.87   $178.85   $178.90  
  Purchase #6 $169.52   8.634%   $184.1564   $184.16   $184.15   $184.20  
  Purchase #7 $150.45   4.655%   $157.4534   $157.45   $157.45   $157.50  
  7 purchase totals = $1,041.63       $1,113.8278   $1,113.82   $1,113.80   $1,114.00