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 $114.67   10.773%   $127.0234   $127.02   $127.00   $127.00  
  Purchase #2 $92.86   3.438%   $96.0525   $96.05   $96.05   $96.10  
  Purchase #3 $134.27   11.285%   $149.4224   $149.42   $149.40   $149.40  
  Purchase #4 $36.75   11.698%   $41.049   $41.05   $41.05   $41.00  
  Purchase #5 $81.77   4.399%   $85.3671   $85.37   $85.35   $85.40  
  Purchase #6 $153.26   6.503%   $163.2265   $163.23   $163.25   $163.20  
  Purchase #7 $71.77   3.641%   $74.3831   $74.38   $74.40   $74.40  
  7 purchase totals = $685.35       $736.5240   $736.52   $736.50   $736.50