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 $243.75   9.762%   $267.5449   $267.54   $267.55   $267.50  
  Purchase #2 $205.65   11.708%   $229.7275   $229.73   $229.75   $229.70  
  Purchase #3 $19.33   4.782%   $20.2544   $20.25   $20.25   $20.30  
  Purchase #4 $36.31   5.745%   $38.396   $38.40   $38.40   $38.40  
  Purchase #5 $229.44   3.599%   $237.6975   $237.70   $237.70   $237.70  
  Purchase #6 $129.40   11.744%   $144.5967   $144.60   $144.60   $144.60  
  Purchase #7 $186.69   11.572%   $208.2938   $208.29   $208.30   $208.30  
  7 purchase totals = $1,050.57       $1,146.5108   $1,146.51   $1,146.55   $1,146.50