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 $164.48   10.861%   $182.3442   $182.34   $182.35   $182.30  
  Purchase #2 $10.84   13.151%   $12.2656   $12.27   $12.25   $12.30  
  Purchase #3 $223.80   3.506%   $231.6464   $231.65   $231.65   $231.60  
  Purchase #4 $248.70   7.425%   $267.166   $267.17   $267.15   $267.20  
  Purchase #5 $111.48   4.701%   $116.7207   $116.72   $116.70   $116.70  
  Purchase #6 $44.64   10.113%   $49.1544   $49.15   $49.15   $49.20  
  Purchase #7 $191.40   13.215%   $216.6935   $216.69   $216.70   $216.70  
  7 purchase totals = $995.34       $1,075.9908   $1,075.99   $1,075.95   $1,076.00