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 $45.87   13.717%   $52.162   $52.16   $52.15   $52.20  
  Purchase #2 $244.49   5.769%   $258.5946   $258.59   $258.60   $258.60  
  Purchase #3 $92.66   3.683%   $96.0727   $96.07   $96.05   $96.10  
  Purchase #4 $141.55   11.627%   $158.008   $158.01   $158.00   $158.00  
  Purchase #5 $244.45   6.765%   $260.987   $260.99   $261.00   $261.00  
  Purchase #6 $110.50   6.290%   $117.4505   $117.45   $117.45   $117.50  
  Purchase #7 $174.41   4.872%   $182.9073   $182.91   $182.90   $182.90  
  7 purchase totals = $1,053.93       $1,126.1821   $1,126.18   $1,126.15   $1,126.30