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 $42.46   5.215%   $44.6743   $44.67   $44.65   $44.70  
  Purchase #2 $192.86   11.582%   $215.197   $215.20   $215.20   $215.20  
  Purchase #3 $127.64   12.332%   $143.3806   $143.38   $143.40   $143.40  
  Purchase #4 $240.73   10.609%   $266.269   $266.27   $266.25   $266.30  
  Purchase #5 $126.95   5.641%   $134.1112   $134.11   $134.10   $134.10  
  Purchase #6 $187.80   4.151%   $195.5956   $195.60   $195.60   $195.60  
  Purchase #7 $103.72   11.129%   $115.263   $115.26   $115.25   $115.30  
  7 purchase totals = $1,022.16       $1,114.4907   $1,114.49   $1,114.45   $1,114.60