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 $72.95   6.183%   $77.4605   $77.46   $77.45   $77.50  
  Purchase #2 $203.72   5.116%   $214.1423   $214.14   $214.15   $214.10  
  Purchase #3 $113.39   13.848%   $129.0922   $129.09   $129.10   $129.10  
  Purchase #4 $17.54   6.518%   $18.6833   $18.68   $18.70   $18.70  
  Purchase #5 $187.95   4.631%   $196.654   $196.65   $196.65   $196.70  
  Purchase #6 $96.78   8.591%   $105.0944   $105.09   $105.10   $105.10  
  Purchase #7 $245.84   11.173%   $273.3077   $273.31   $273.30   $273.30  
  7 purchase totals = $938.17       $1,014.4344   $1,014.42   $1,014.45   $1,014.50