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 $118.91   13.317%   $134.7452   $134.75   $134.75   $134.70  
  Purchase #2 $96.87   13.869%   $110.3049   $110.30   $110.30   $110.30  
  Purchase #3 $136.76   12.842%   $154.3227   $154.32   $154.30   $154.30  
  Purchase #4 $164.97   6.541%   $175.7607   $175.76   $175.75   $175.80  
  Purchase #5 $166.69   3.606%   $172.7008   $172.70   $172.70   $172.70  
  Purchase #6 $168.84   7.806%   $182.0197   $182.02   $182.00   $182.00  
  Purchase #7 $111.59   6.382%   $118.7117   $118.71   $118.70   $118.70  
  7 purchase totals = $964.63       $1,048.5657   $1,048.56   $1,048.50   $1,048.50