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 $205.57   10.569%   $227.2967   $227.30   $227.30   $227.30  
  Purchase #2 $246.51   7.366%   $264.6679   $264.67   $264.65   $264.70  
  Purchase #3 $44.65   8.416%   $48.4077   $48.41   $48.40   $48.40  
  Purchase #4 $234.81   3.106%   $242.1032   $242.10   $242.10   $242.10  
  Purchase #5 $232.41   10.570%   $256.9757   $256.98   $257.00   $257.00  
  Purchase #6 $249.71   9.619%   $273.7296   $273.73   $273.75   $273.70  
  Purchase #7 $193.28   8.397%   $209.5097   $209.51   $209.50   $209.50  
  7 purchase totals = $1,406.94       $1,522.6905   $1,522.70   $1,522.70   $1,522.70