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 $208.65   8.798%   $227.007   $227.01   $227.00   $227.00  
  Purchase #2 $197.59   5.688%   $208.8289   $208.83   $208.85   $208.80  
  Purchase #3 $21.36   13.499%   $24.2434   $24.24   $24.25   $24.20  
  Purchase #4 $23.50   3.586%   $24.3427   $24.34   $24.35   $24.30  
  Purchase #5 $209.33   7.551%   $225.1365   $225.14   $225.15   $225.10  
  Purchase #6 $185.87   12.788%   $209.6391   $209.64   $209.65   $209.60  
  Purchase #7 $119.81   12.170%   $134.3909   $134.39   $134.40   $134.40  
  7 purchase totals = $966.11       $1,053.5885   $1,053.59   $1,053.65   $1,053.40