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 $245.81   6.692%   $262.2596   $262.26   $262.25   $262.30  
  Purchase #2 $198.79   4.506%   $207.7475   $207.75   $207.75   $207.70  
  Purchase #3 $83.88   12.787%   $94.6057   $94.61   $94.60   $94.60  
  Purchase #4 $171.33   7.408%   $184.0221   $184.02   $184.00   $184.00  
  Purchase #5 $199.50   4.509%   $208.4955   $208.50   $208.50   $208.50  
  Purchase #6 $37.54   8.851%   $40.8627   $40.86   $40.85   $40.90  
  Purchase #7 $49.65   11.189%   $55.2053   $55.21   $55.20   $55.20  
  7 purchase totals = $986.50       $1,053.1984   $1,053.21   $1,053.15   $1,053.20