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 $41.82   11.659%   $46.6958   $46.70   $46.70   $46.70  
  Purchase #2 $175.62   8.504%   $190.5547   $190.55   $190.55   $190.60  
  Purchase #3 $121.29   3.164%   $125.1276   $125.13   $125.15   $125.10  
  Purchase #4 $227.73   5.516%   $240.2916   $240.29   $240.30   $240.30  
  Purchase #5 $235.77   5.670%   $249.1382   $249.14   $249.15   $249.10  
  Purchase #6 $191.98   13.498%   $217.8935   $217.89   $217.90   $217.90  
  Purchase #7 $33.73   13.520%   $38.2903   $38.29   $38.30   $38.30  
  7 purchase totals = $1,027.94       $1,107.9917   $1,107.99   $1,108.05   $1,108.00