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 $216.67   11.235%   $241.0129   $241.01   $241.00   $241.00  
  Purchase #2 $43.69   10.278%   $48.1805   $48.18   $48.20   $48.20  
  Purchase #3 $170.28   10.446%   $188.0674   $188.07   $188.05   $188.10  
  Purchase #4 $178.42   11.466%   $198.8776   $198.88   $198.90   $198.90  
  Purchase #5 $243.55   9.420%   $266.4924   $266.49   $266.50   $266.50  
  Purchase #6 $155.96   5.303%   $164.2306   $164.23   $164.25   $164.20  
  Purchase #7 $222.99   11.289%   $248.1633   $248.16   $248.15   $248.20  
  7 purchase totals = $1,231.56       $1,355.0247   $1,355.02   $1,355.05   $1,355.10