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 $169.81   12.255%   $190.6202   $190.62   $190.60   $190.60  
  Purchase #2 $186.93   10.648%   $206.8343   $206.83   $206.85   $206.80  
  Purchase #3 $49.72   10.670%   $55.0251   $55.03   $55.05   $55.00  
  Purchase #4 $112.88   5.234%   $118.7881   $118.79   $118.80   $118.80  
  Purchase #5 $212.48   8.187%   $229.8757   $229.88   $229.90   $229.90  
  Purchase #6 $50.57   9.280%   $55.2629   $55.26   $55.25   $55.30  
  Purchase #7 $200.60   8.458%   $217.5667   $217.57   $217.55   $217.60  
  7 purchase totals = $982.99       $1,073.9730   $1,073.98   $1,074.00   $1,074.00