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 $65.58   13.524%   $74.449   $74.45   $74.45   $74.40  
  Purchase #2 $115.47   9.108%   $125.987   $125.99   $126.00   $126.00  
  Purchase #3 $180.85   9.509%   $198.047   $198.05   $198.05   $198.00  
  Purchase #4 $236.77   11.138%   $263.1414   $263.14   $263.15   $263.10  
  Purchase #5 $196.28   12.732%   $221.2704   $221.27   $221.25   $221.30  
  Purchase #6 $202.77   8.266%   $219.531   $219.53   $219.55   $219.50  
  Purchase #7 $62.85   10.461%   $69.4247   $69.42   $69.40   $69.40  
  7 purchase totals = $1,060.57       $1,171.8505   $1,171.85   $1,171.85   $1,171.70