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 $184.94   5.580%   $195.2597   $195.26   $195.25   $195.30  
  Purchase #2 $117.67   6.341%   $125.1315   $125.13   $125.15   $125.10  
  Purchase #3 $178.97   4.291%   $186.6496   $186.65   $186.65   $186.60  
  Purchase #4 $34.37   11.407%   $38.2906   $38.29   $38.30   $38.30  
  Purchase #5 $186.92   5.158%   $196.5613   $196.56   $196.55   $196.60  
  Purchase #6 $71.47   3.207%   $73.762   $73.76   $73.75   $73.80  
  Purchase #7 $238.92   4.554%   $249.8004   $249.80   $249.80   $249.80  
  7 purchase totals = $1,013.26       $1,065.4551   $1,065.45   $1,065.45   $1,065.50