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 $244.86   9.332%   $267.7103   $267.71   $267.70   $267.70  
  Purchase #2 $198.65   11.466%   $221.4272   $221.43   $221.45   $221.40  
  Purchase #3 $196.33   5.589%   $207.3029   $207.30   $207.30   $207.30  
  Purchase #4 $33.76   8.803%   $36.7319   $36.73   $36.75   $36.70  
  Purchase #5 $10.87   5.205%   $11.4358   $11.44   $11.45   $11.40  
  Purchase #6 $248.46   3.449%   $257.0294   $257.03   $257.05   $257.00  
  Purchase #7 $165.30   9.390%   $180.8217   $180.82   $180.80   $180.80  
  7 purchase totals = $1,098.23       $1,182.4592   $1,182.46   $1,182.50   $1,182.30