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 $216.75   13.243%   $245.4542   $245.45   $245.45   $245.50  
  Purchase #2 $225.96   8.528%   $245.2299   $245.23   $245.25   $245.20  
  Purchase #3 $167.36   5.726%   $176.943   $176.94   $176.95   $176.90  
  Purchase #4 $142.70   6.616%   $152.141   $152.14   $152.15   $152.10  
  Purchase #5 $110.93   11.358%   $123.5294   $123.53   $123.55   $123.50  
  Purchase #6 $153.45   4.287%   $160.0284   $160.03   $160.05   $160.00  
  Purchase #7 $116.87   5.240%   $122.994   $122.99   $123.00   $123.00  
  7 purchase totals = $1,134.02       $1,226.3199   $1,226.31   $1,226.40   $1,226.20