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 $146.26   4.852%   $153.3565   $153.36   $153.35   $153.40  
  Purchase #2 $188.46   12.622%   $212.2474   $212.25   $212.25   $212.20  
  Purchase #3 $68.98   6.483%   $73.452   $73.45   $73.45   $73.50  
  Purchase #4 $94.57   3.826%   $98.1882   $98.19   $98.20   $98.20  
  Purchase #5 $100.28   4.393%   $104.6853   $104.69   $104.70   $104.70  
  Purchase #6 $54.61   11.791%   $61.0491   $61.05   $61.05   $61.00  
  Purchase #7 $68.92   10.311%   $76.0263   $76.03   $76.05   $76.00  
  7 purchase totals = $722.08       $779.0048   $779.02   $779.05   $779.00