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 $67.36   13.753%   $76.624   $76.62   $76.60   $76.60  
  Purchase #2 $196.74   6.156%   $208.8513   $208.85   $208.85   $208.90  
  Purchase #3 $192.34   5.449%   $202.8206   $202.82   $202.80   $202.80  
  Purchase #4 $243.55   9.381%   $266.3974   $266.40   $266.40   $266.40  
  Purchase #5 $174.95   11.865%   $195.7078   $195.71   $195.70   $195.70  
  Purchase #6 $182.88   3.155%   $188.6499   $188.65   $188.65   $188.60  
  Purchase #7 $105.63   10.204%   $116.4085   $116.41   $116.40   $116.40  
  7 purchase totals = $1,163.45       $1,255.4595   $1,255.46   $1,255.40   $1,255.40