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 $188.74   3.627%   $195.5856   $195.59   $195.60   $195.60  
  Purchase #2 $21.95   13.414%   $24.8944   $24.89   $24.90   $24.90  
  Purchase #3 $161.92   11.722%   $180.9003   $180.90   $180.90   $180.90  
  Purchase #4 $52.60   6.528%   $56.0337   $56.03   $56.05   $56.00  
  Purchase #5 $192.56   11.622%   $214.9393   $214.94   $214.95   $214.90  
  Purchase #6 $216.25   10.180%   $238.2643   $238.26   $238.25   $238.30  
  Purchase #7 $108.56   5.594%   $114.6328   $114.63   $114.65   $114.60  
  7 purchase totals = $942.58       $1,025.2504   $1,025.24   $1,025.30   $1,025.20