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 $187.38   10.605%   $207.2516   $207.25   $207.25   $207.30  
  Purchase #2 $154.66   6.448%   $164.6325   $164.63   $164.65   $164.60  
  Purchase #3 $195.99   10.137%   $215.8575   $215.86   $215.85   $215.90  
  Purchase #4 $46.39   11.703%   $51.819   $51.82   $51.80   $51.80  
  Purchase #5 $222.59   5.688%   $235.2509   $235.25   $235.25   $235.30  
  Purchase #6 $83.40   11.146%   $92.6958   $92.70   $92.70   $92.70  
  Purchase #7 $133.77   11.225%   $148.7857   $148.79   $148.80   $148.80  
  7 purchase totals = $1,024.18       $1,116.2930   $1,116.30   $1,116.30   $1,116.40