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 $104.74   9.758%   $114.9605   $114.96   $114.95   $115.00  
  Purchase #2 $109.36   4.113%   $113.858   $113.86   $113.85   $113.90  
  Purchase #3 $53.93   7.514%   $57.9823   $57.98   $58.00   $58.00  
  Purchase #4 $14.52   3.709%   $15.0585   $15.06   $15.05   $15.10  
  Purchase #5 $169.30   3.298%   $174.8835   $174.88   $174.90   $174.90  
  Purchase #6 $206.31   10.288%   $227.5352   $227.54   $227.55   $227.50  
  Purchase #7 $207.38   5.704%   $219.209   $219.21   $219.20   $219.20  
  7 purchase totals = $865.54       $923.4870   $923.49   $923.50   $923.60