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 $68.38   7.750%   $73.6795   $73.68   $73.70   $73.70  
  Purchase #2 $86.26   11.105%   $95.8392   $95.84   $95.85   $95.80  
  Purchase #3 $145.41   4.265%   $151.6117   $151.61   $151.60   $151.60  
  Purchase #4 $77.62   6.775%   $82.8788   $82.88   $82.90   $82.90  
  Purchase #5 $210.70   11.203%   $234.3047   $234.30   $234.30   $234.30  
  Purchase #6 $208.25   7.609%   $224.0957   $224.10   $224.10   $224.10  
  Purchase #7 $177.34   4.126%   $184.657   $184.66   $184.65   $184.70  
  7 purchase totals = $973.96       $1,047.0666   $1,047.07   $1,047.10   $1,047.10