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 $200.62   7.138%   $214.9403   $214.94   $214.95   $214.90  
  Purchase #2 $237.47   3.235%   $245.1522   $245.15   $245.15   $245.20  
  Purchase #3 $164.36   7.872%   $177.2984   $177.30   $177.30   $177.30  
  Purchase #4 $141.33   4.712%   $147.9895   $147.99   $148.00   $148.00  
  Purchase #5 $58.66   3.241%   $60.5612   $60.56   $60.55   $60.60  
  Purchase #6 $120.40   4.288%   $125.5628   $125.56   $125.55   $125.60  
  Purchase #7 $175.83   5.861%   $186.1354   $186.14   $186.15   $186.10  
  7 purchase totals = $1,098.67       $1,157.6398   $1,157.64   $1,157.65   $1,157.70