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 $176.26   8.676%   $191.5523   $191.55   $191.55   $191.60  
  Purchase #2 $189.78   11.293%   $211.2119   $211.21   $211.20   $211.20  
  Purchase #3 $49.36   10.348%   $54.4678   $54.47   $54.45   $54.50  
  Purchase #4 $175.89   9.788%   $193.1061   $193.11   $193.10   $193.10  
  Purchase #5 $224.43   12.837%   $253.2401   $253.24   $253.25   $253.20  
  Purchase #6 $157.59   3.639%   $163.3247   $163.32   $163.30   $163.30  
  Purchase #7 $92.76   9.342%   $101.4256   $101.43   $101.45   $101.40  
  7 purchase totals = $1,066.07       $1,168.3285   $1,168.33   $1,168.30   $1,168.30