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 $208.73   8.624%   $226.7309   $226.73   $226.75   $226.70  
  Purchase #2 $215.82   6.453%   $229.7469   $229.75   $229.75   $229.70  
  Purchase #3 $68.90   3.305%   $71.1771   $71.18   $71.20   $71.20  
  Purchase #4 $247.41   6.430%   $263.3185   $263.32   $263.30   $263.30  
  Purchase #5 $117.94   9.409%   $129.037   $129.04   $129.05   $129.00  
  Purchase #6 $69.75   10.351%   $76.9698   $76.97   $76.95   $77.00  
  Purchase #7 $44.85   8.388%   $48.612   $48.61   $48.60   $48.60  
  7 purchase totals = $973.40       $1,045.5922   $1,045.60   $1,045.60   $1,045.50