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 $102.88   13.376%   $116.6412   $116.64   $116.65   $116.60  
  Purchase #2 $200.28   3.133%   $206.5548   $206.55   $206.55   $206.60  
  Purchase #3 $119.25   4.572%   $124.7021   $124.70   $124.70   $124.70  
  Purchase #4 $166.57   4.209%   $173.5809   $173.58   $173.60   $173.60  
  Purchase #5 $135.41   6.750%   $144.5502   $144.55   $144.55   $144.60  
  Purchase #6 $244.35   3.868%   $253.8015   $253.80   $253.80   $253.80  
  Purchase #7 $196.42   5.582%   $207.3842   $207.38   $207.40   $207.40  
  7 purchase totals = $1,165.16       $1,227.2149   $1,227.20   $1,227.25   $1,227.30