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 $164.38   13.546%   $186.6469   $186.65   $186.65   $186.60  
  Purchase #2 $235.88   4.144%   $245.6549   $245.65   $245.65   $245.70  
  Purchase #3 $169.87   8.136%   $183.6906   $183.69   $183.70   $183.70  
  Purchase #4 $220.40   6.210%   $234.0868   $234.09   $234.10   $234.10  
  Purchase #5 $105.40   5.855%   $111.5712   $111.57   $111.55   $111.60  
  Purchase #6 $69.39   7.103%   $74.3188   $74.32   $74.30   $74.30  
  Purchase #7 $108.91   10.410%   $120.2475   $120.25   $120.25   $120.20  
  7 purchase totals = $1,074.23       $1,156.2167   $1,156.22   $1,156.20   $1,156.20