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 $176.54   10.739%   $195.4986   $195.50   $195.50   $195.50  
  Purchase #2 $212.71   6.567%   $226.6787   $226.68   $226.70   $226.70  
  Purchase #3 $247.64   3.189%   $255.5372   $255.54   $255.55   $255.50  
  Purchase #4 $41.37   11.365%   $46.0717   $46.07   $46.05   $46.10  
  Purchase #5 $11.91   10.119%   $13.1152   $13.12   $13.10   $13.10  
  Purchase #6 $101.30   10.743%   $112.1827   $112.18   $112.20   $112.20  
  Purchase #7 $196.32   10.150%   $216.2465   $216.25   $216.25   $216.20  
  7 purchase totals = $987.79       $1,065.3306   $1,065.34   $1,065.35   $1,065.30