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 $196.74   5.704%   $207.962   $207.96   $207.95   $208.00  
  Purchase #2 $219.28   4.139%   $228.356   $228.36   $228.35   $228.40  
  Purchase #3 $58.26   11.423%   $64.915   $64.92   $64.90   $64.90  
  Purchase #4 $129.96   8.533%   $141.0495   $141.05   $141.05   $141.00  
  Purchase #5 $21.30   13.434%   $24.1614   $24.16   $24.15   $24.20  
  Purchase #6 $116.31   13.460%   $131.9653   $131.97   $131.95   $132.00  
  Purchase #7 $33.73   10.103%   $37.1377   $37.14   $37.15   $37.10  
  7 purchase totals = $775.58       $835.5469   $835.56   $835.50   $835.60