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 $163.94   13.626%   $186.2785   $186.28   $186.30   $186.30  
  Purchase #2 $34.72   4.311%   $36.2168   $36.22   $36.20   $36.20  
  Purchase #3 $187.52   7.458%   $201.5052   $201.51   $201.50   $201.50  
  Purchase #4 $158.97   10.826%   $176.1801   $176.18   $176.20   $176.20  
  Purchase #5 $221.81   5.625%   $234.2868   $234.29   $234.30   $234.30  
  Purchase #6 $186.50   11.194%   $207.3768   $207.38   $207.40   $207.40  
  Purchase #7 $201.94   9.466%   $221.0556   $221.06   $221.05   $221.10  
  7 purchase totals = $1,155.40       $1,262.8998   $1,262.92   $1,262.95   $1,263.00