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 $207.46   8.731%   $225.5733   $225.57   $225.55   $225.60  
  Purchase #2 $237.86   11.697%   $265.6825   $265.68   $265.70   $265.70  
  Purchase #3 $213.83   10.470%   $236.218   $236.22   $236.20   $236.20  
  Purchase #4 $87.53   6.712%   $93.405   $93.41   $93.40   $93.40  
  Purchase #5 $240.48   3.476%   $248.8391   $248.84   $248.85   $248.80  
  Purchase #6 $158.78   3.215%   $163.8848   $163.88   $163.90   $163.90  
  Purchase #7 $121.52   11.819%   $135.8824   $135.88   $135.90   $135.90  
  7 purchase totals = $1,267.46       $1,369.4851   $1,369.48   $1,369.50   $1,369.50