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 $185.29   11.729%   $207.0227   $207.02   $207.00   $207.00  
  Purchase #2 $212.52   5.683%   $224.5975   $224.60   $224.60   $224.60  
  Purchase #3 $55.39   6.317%   $58.889   $58.89   $58.90   $58.90  
  Purchase #4 $239.60   9.242%   $261.7438   $261.74   $261.75   $261.70  
  Purchase #5 $130.51   8.301%   $141.3436   $141.34   $141.35   $141.30  
  Purchase #6 $105.75   10.642%   $117.0039   $117.00   $117.00   $117.00  
  Purchase #7 $140.38   7.609%   $151.0615   $151.06   $151.05   $151.10  
  7 purchase totals = $1,069.44       $1,161.6620   $1,161.65   $1,161.65   $1,161.60