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 $37.69   10.498%   $41.6467   $41.65   $41.65   $41.60  
  Purchase #2 $26.76   5.132%   $28.1333   $28.13   $28.15   $28.10  
  Purchase #3 $106.90   3.784%   $110.9451   $110.95   $110.95   $110.90  
  Purchase #4 $146.34   11.348%   $162.9467   $162.95   $162.95   $162.90  
  Purchase #5 $246.86   6.379%   $262.6072   $262.61   $262.60   $262.60  
  Purchase #6 $95.55   11.219%   $106.2698   $106.27   $106.25   $106.30  
  Purchase #7 $224.61   6.683%   $239.6207   $239.62   $239.60   $239.60  
  7 purchase totals = $884.71       $952.1695   $952.18   $952.15   $952.00