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 $56.67   9.264%   $61.9199   $61.92   $61.90   $61.90  
  Purchase #2 $222.54   8.142%   $240.6592   $240.66   $240.65   $240.70  
  Purchase #3 $144.51   9.325%   $157.9856   $157.99   $158.00   $158.00  
  Purchase #4 $127.37   10.258%   $140.4356   $140.44   $140.45   $140.40  
  Purchase #5 $120.31   10.621%   $133.0881   $133.09   $133.10   $133.10  
  Purchase #6 $247.69   7.793%   $266.9925   $266.99   $267.00   $267.00  
  Purchase #7 $174.85   5.314%   $184.1415   $184.14   $184.15   $184.10  
  7 purchase totals = $1,093.94       $1,185.2224   $1,185.23   $1,185.25   $1,185.20