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 $84.27   13.477%   $95.6271   $95.63   $95.65   $95.60  
  Purchase #2 $147.75   10.269%   $162.9224   $162.92   $162.90   $162.90  
  Purchase #3 $96.77   5.830%   $102.4117   $102.41   $102.40   $102.40  
  Purchase #4 $108.90   3.482%   $112.6919   $112.69   $112.70   $112.70  
  Purchase #5 $203.78   10.520%   $225.2177   $225.22   $225.20   $225.20  
  Purchase #6 $48.76   6.304%   $51.8338   $51.83   $51.85   $51.80  
  Purchase #7 $112.40   12.460%   $126.405   $126.41   $126.40   $126.40  
  7 purchase totals = $802.63       $877.1096   $877.11   $877.10   $877.00