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 $195.26   3.195%   $201.4986   $201.50   $201.50   $201.50  
  Purchase #2 $207.77   6.342%   $220.9468   $220.95   $220.95   $220.90  
  Purchase #3 $201.84   6.499%   $214.9576   $214.96   $214.95   $215.00  
  Purchase #4 $106.86   6.643%   $113.9587   $113.96   $113.95   $114.00  
  Purchase #5 $95.28   10.496%   $105.2806   $105.28   $105.30   $105.30  
  Purchase #6 $5.68   10.164%   $6.2573   $6.26   $6.25   $6.30  
  Purchase #7 $158.97   4.794%   $166.591   $166.59   $166.60   $166.60  
  7 purchase totals = $971.66       $1,029.4906   $1,029.50   $1,029.50   $1,029.60