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 $56.31   9.801%   $61.8289   $61.83   $61.85   $61.80  
  Purchase #2 $144.99   5.633%   $153.1573   $153.16   $153.15   $153.20  
  Purchase #3 $196.89   11.228%   $218.9968   $219.00   $219.00   $219.00  
  Purchase #4 $69.37   9.517%   $75.9719   $75.97   $75.95   $76.00  
  Purchase #5 $231.63   13.661%   $263.273   $263.27   $263.25   $263.30  
  Purchase #6 $158.38   6.250%   $168.2788   $168.28   $168.30   $168.30  
  Purchase #7 $248.51   7.187%   $266.3704   $266.37   $266.35   $266.40  
  7 purchase totals = $1,106.08       $1,207.8771   $1,207.88   $1,207.85   $1,208.00