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 $228.60   7.675%   $246.1451   $246.15   $246.15   $246.10  
  Purchase #2 $20.44   13.495%   $23.1984   $23.20   $23.20   $23.20  
  Purchase #3 $77.71   8.315%   $84.1716   $84.17   $84.15   $84.20  
  Purchase #4 $226.94   9.541%   $248.5923   $248.59   $248.60   $248.60  
  Purchase #5 $141.69   8.125%   $153.2023   $153.20   $153.20   $153.20  
  Purchase #6 $93.55   12.620%   $105.356   $105.36   $105.35   $105.40  
  Purchase #7 $96.30   10.641%   $106.5473   $106.55   $106.55   $106.50  
  7 purchase totals = $885.23       $967.2130   $967.22   $967.20   $967.20