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 $242.58   8.257%   $262.6098   $262.61   $262.60   $262.60  
  Purchase #2 $33.79   7.584%   $36.3526   $36.35   $36.35   $36.40  
  Purchase #3 $197.31   8.651%   $214.3793   $214.38   $214.40   $214.40  
  Purchase #4 $18.90   6.657%   $20.1582   $20.16   $20.15   $20.20  
  Purchase #5 $81.72   6.202%   $86.7883   $86.79   $86.80   $86.80  
  Purchase #6 $223.96   4.331%   $233.6597   $233.66   $233.65   $233.70  
  Purchase #7 $246.92   6.381%   $262.676   $262.68   $262.70   $262.70  
  7 purchase totals = $1,045.18       $1,116.6239   $1,116.63   $1,116.65   $1,116.80