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 $243.55   7.591%   $262.0379   $262.04   $262.05   $262.00  
  Purchase #2 $115.47   8.841%   $125.6787   $125.68   $125.70   $125.70  
  Purchase #3 $178.66   7.568%   $192.181   $192.18   $192.20   $192.20  
  Purchase #4 $198.72   5.537%   $209.7231   $209.72   $209.70   $209.70  
  Purchase #5 $207.96   3.683%   $215.6192   $215.62   $215.60   $215.60  
  Purchase #6 $14.83   11.380%   $16.5177   $16.52   $16.50   $16.50  
  Purchase #7 $158.64   3.102%   $163.561   $163.56   $163.55   $163.60  
  7 purchase totals = $1,117.83       $1,185.3186   $1,185.32   $1,185.30   $1,185.30