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 $194.76   6.605%   $207.6239   $207.62   $207.60   $207.60  
  Purchase #2 $108.74   7.787%   $117.2076   $117.21   $117.20   $117.20  
  Purchase #3 $214.39   5.659%   $226.5223   $226.52   $226.50   $226.50  
  Purchase #4 $196.62   8.661%   $213.6493   $213.65   $213.65   $213.60  
  Purchase #5 $192.87   11.692%   $215.4204   $215.42   $215.40   $215.40  
  Purchase #6 $67.79   11.845%   $75.8197   $75.82   $75.80   $75.80  
  Purchase #7 $121.99   3.639%   $126.4292   $126.43   $126.45   $126.40  
  7 purchase totals = $1,097.16       $1,182.6724   $1,182.67   $1,182.60   $1,182.50