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 $58.36   8.134%   $63.107   $63.11   $63.10   $63.10  
  Purchase #2 $178.61   8.461%   $193.7222   $193.72   $193.70   $193.70  
  Purchase #3 $85.32   3.811%   $88.5715   $88.57   $88.55   $88.60  
  Purchase #4 $215.68   11.237%   $239.916   $239.92   $239.90   $239.90  
  Purchase #5 $107.54   10.792%   $119.1457   $119.15   $119.15   $119.10  
  Purchase #6 $219.30   6.423%   $233.3856   $233.39   $233.40   $233.40  
  Purchase #7 $220.87   11.293%   $245.8128   $245.81   $245.80   $245.80  
  7 purchase totals = $1,085.68       $1,183.6608   $1,183.67   $1,183.60   $1,183.60