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 $211.25   7.786%   $227.6979   $227.70   $227.70   $227.70  
  Purchase #2 $194.28   11.824%   $217.2517   $217.25   $217.25   $217.30  
  Purchase #3 $236.84   8.442%   $256.834   $256.83   $256.85   $256.80  
  Purchase #4 $174.68   11.801%   $195.294   $195.29   $195.30   $195.30  
  Purchase #5 $246.64   10.594%   $272.769   $272.77   $272.75   $272.80  
  Purchase #6 $194.92   8.290%   $211.0789   $211.08   $211.10   $211.10  
  Purchase #7 $81.66   8.352%   $88.4802   $88.48   $88.50   $88.50  
  7 purchase totals = $1,340.27       $1,469.4057   $1,469.40   $1,469.45   $1,469.50