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 $217.94   9.224%   $238.0428   $238.04   $238.05   $238.00  
  Purchase #2 $188.39   9.345%   $205.995   $206.00   $206.00   $206.00  
  Purchase #3 $61.57   11.852%   $68.8673   $68.87   $68.85   $68.90  
  Purchase #4 $152.38   9.513%   $166.8759   $166.88   $166.90   $166.90  
  Purchase #5 $114.69   13.826%   $130.547   $130.55   $130.55   $130.50  
  Purchase #6 $177.29   5.233%   $186.5676   $186.57   $186.55   $186.60  
  Purchase #7 $185.39   12.798%   $209.1162   $209.12   $209.10   $209.10  
  7 purchase totals = $1,097.65       $1,206.0118   $1,206.03   $1,206.00   $1,206.00