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 $190.61   8.726%   $207.2426   $207.24   $207.25   $207.20  
  Purchase #2 $198.69   5.617%   $209.8504   $209.85   $209.85   $209.90  
  Purchase #3 $98.53   6.334%   $104.7709   $104.77   $104.75   $104.80  
  Purchase #4 $147.60   3.159%   $152.2627   $152.26   $152.25   $152.30  
  Purchase #5 $200.58   8.813%   $218.2571   $218.26   $218.25   $218.30  
  Purchase #6 $106.48   11.450%   $118.672   $118.67   $118.65   $118.70  
  Purchase #7 $180.92   6.545%   $192.7612   $192.76   $192.75   $192.80  
  7 purchase totals = $1,123.41       $1,203.8169   $1,203.81   $1,203.75   $1,204.00