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 $174.41   12.727%   $196.6072   $196.61   $196.60   $196.60  
  Purchase #2 $192.61   13.173%   $217.9825   $217.98   $218.00   $218.00  
  Purchase #3 $67.36   5.717%   $71.211   $71.21   $71.20   $71.20  
  Purchase #4 $64.94   7.166%   $69.5936   $69.59   $69.60   $69.60  
  Purchase #5 $107.36   4.624%   $112.3243   $112.32   $112.30   $112.30  
  Purchase #6 $26.90   3.509%   $27.8439   $27.84   $27.85   $27.80  
  Purchase #7 $58.48   3.658%   $60.6192   $60.62   $60.60   $60.60  
  7 purchase totals = $692.06       $756.1817   $756.17   $756.15   $756.10