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 $41.51   6.719%   $44.2991   $44.30   $44.30   $44.30  
  Purchase #2 $215.67   7.432%   $231.6986   $231.70   $231.70   $231.70  
  Purchase #3 $126.95   6.198%   $134.8184   $134.82   $134.80   $134.80  
  Purchase #4 $220.63   12.816%   $248.9059   $248.91   $248.90   $248.90  
  Purchase #5 $197.94   5.301%   $208.4328   $208.43   $208.45   $208.40  
  Purchase #6 $56.58   7.476%   $60.8099   $60.81   $60.80   $60.80  
  Purchase #7 $242.27   13.531%   $275.0516   $275.05   $275.05   $275.10  
  7 purchase totals = $1,101.55       $1,204.0163   $1,204.02   $1,204.00   $1,204.00