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 $163.38   6.824%   $174.5291   $174.53   $174.55   $174.50  
  Purchase #2 $225.41   10.786%   $249.7227   $249.72   $249.70   $249.70  
  Purchase #3 $45.27   9.680%   $49.6521   $49.65   $49.65   $49.70  
  Purchase #4 $184.30   11.694%   $205.852   $205.85   $205.85   $205.90  
  Purchase #5 $245.72   9.432%   $268.8963   $268.90   $268.90   $268.90  
  Purchase #6 $202.68   6.531%   $215.917   $215.92   $215.90   $215.90  
  Purchase #7 $186.56   3.817%   $193.681   $193.68   $193.70   $193.70  
  7 purchase totals = $1,253.32       $1,358.2502   $1,358.25   $1,358.25   $1,358.30