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 $239.26   10.829%   $265.1695   $265.17   $265.15   $265.20  
  Purchase #2 $111.37   5.635%   $117.6457   $117.65   $117.65   $117.60  
  Purchase #3 $146.30   4.310%   $152.6055   $152.61   $152.60   $152.60  
  Purchase #4 $132.94   8.852%   $144.7078   $144.71   $144.70   $144.70  
  Purchase #5 $169.88   7.446%   $182.5293   $182.53   $182.55   $182.50  
  Purchase #6 $181.38   12.249%   $203.5972   $203.60   $203.60   $203.60  
  Purchase #7 $139.40   3.553%   $144.3529   $144.35   $144.35   $144.40  
  7 purchase totals = $1,120.53       $1,210.6079   $1,210.62   $1,210.60   $1,210.60