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 $61.87   9.480%   $67.7353   $67.74   $67.75   $67.70  
  Purchase #2 $190.34   9.700%   $208.803   $208.80   $208.80   $208.80  
  Purchase #3 $92.99   3.169%   $95.9369   $95.94   $95.95   $95.90  
  Purchase #4 $158.62   10.355%   $175.0451   $175.05   $175.05   $175.00  
  Purchase #5 $214.91   5.679%   $227.1147   $227.11   $227.10   $227.10  
  Purchase #6 $217.65   7.827%   $234.6855   $234.69   $234.70   $234.70  
  Purchase #7 $63.49   3.837%   $65.9261   $65.93   $65.95   $65.90  
  7 purchase totals = $999.87       $1,075.2466   $1,075.26   $1,075.30   $1,075.10