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 $43.83   9.683%   $48.0741   $48.07   $48.05   $48.10  
  Purchase #2 $136.94   11.709%   $152.9743   $152.97   $152.95   $153.00  
  Purchase #3 $70.60   11.462%   $78.6922   $78.69   $78.70   $78.70  
  Purchase #4 $91.55   8.114%   $98.9784   $98.98   $99.00   $99.00  
  Purchase #5 $151.70   10.215%   $167.1962   $167.20   $167.20   $167.20  
  Purchase #6 $54.96   6.252%   $58.3961   $58.40   $58.40   $58.40  
  Purchase #7 $146.45   3.539%   $151.6329   $151.63   $151.65   $151.60  
  7 purchase totals = $696.03       $755.9442   $755.94   $755.95   $756.00