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 $227.28   7.632%   $244.626   $244.63   $244.65   $244.60  
  Purchase #2 $62.83   9.284%   $68.6631   $68.66   $68.65   $68.70  
  Purchase #3 $156.25   11.554%   $174.3031   $174.30   $174.30   $174.30  
  Purchase #4 $84.92   9.734%   $93.1861   $93.19   $93.20   $93.20  
  Purchase #5 $204.29   11.237%   $227.2461   $227.25   $227.25   $227.20  
  Purchase #6 $232.55   4.138%   $242.1729   $242.17   $242.15   $242.20  
  Purchase #7 $16.69   3.615%   $17.2933   $17.29   $17.30   $17.30  
  7 purchase totals = $984.81       $1,067.4906   $1,067.49   $1,067.50   $1,067.50