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 $68.26   9.260%   $74.5809   $74.58   $74.60   $74.60  
  Purchase #2 $207.76   5.104%   $218.3641   $218.36   $218.35   $218.40  
  Purchase #3 $220.76   12.387%   $248.1055   $248.11   $248.10   $248.10  
  Purchase #4 $149.43   6.621%   $159.3238   $159.32   $159.30   $159.30  
  Purchase #5 $129.90   12.436%   $146.0544   $146.05   $146.05   $146.10  
  Purchase #6 $119.31   8.134%   $129.0147   $129.01   $129.00   $129.00  
  Purchase #7 $79.47   8.359%   $86.1129   $86.11   $86.10   $86.10  
  7 purchase totals = $974.89       $1,061.5563   $1,061.54   $1,061.50   $1,061.60