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 $212.53   5.788%   $224.8312   $224.83   $224.85   $224.80  
  Purchase #2 $68.31   3.544%   $70.7309   $70.73   $70.75   $70.70  
  Purchase #3 $239.39   11.602%   $267.164   $267.16   $267.15   $267.20  
  Purchase #4 $207.64   8.688%   $225.6798   $225.68   $225.70   $225.70  
  Purchase #5 $93.30   5.278%   $98.2244   $98.22   $98.20   $98.20  
  Purchase #6 $214.44   6.364%   $228.087   $228.09   $228.10   $228.10  
  Purchase #7 $59.48   4.237%   $62.0002   $62.00   $62.00   $62.00  
  7 purchase totals = $1,095.09       $1,176.7175   $1,176.71   $1,176.75   $1,176.70