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 $208.46   7.548%   $224.1946   $224.19   $224.20   $224.20  
  Purchase #2 $48.84   6.422%   $51.9765   $51.98   $52.00   $52.00  
  Purchase #3 $244.78   3.783%   $254.04   $254.04   $254.05   $254.00  
  Purchase #4 $20.26   4.396%   $21.1506   $21.15   $21.15   $21.20  
  Purchase #5 $173.99   10.713%   $192.6295   $192.63   $192.65   $192.60  
  Purchase #6 $214.56   6.708%   $228.9527   $228.95   $228.95   $229.00  
  Purchase #7 $126.70   8.558%   $137.543   $137.54   $137.55   $137.50  
  7 purchase totals = $1,037.59       $1,110.4869   $1,110.48   $1,110.55   $1,110.50