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 $232.57   11.139%   $258.476   $258.48   $258.50   $258.50  
  Purchase #2 $181.81   7.383%   $195.233   $195.23   $195.25   $195.20  
  Purchase #3 $112.48   6.862%   $120.1984   $120.20   $120.20   $120.20  
  Purchase #4 $151.98   12.688%   $171.2632   $171.26   $171.25   $171.30  
  Purchase #5 $183.99   6.623%   $196.1757   $196.18   $196.20   $196.20  
  Purchase #6 $202.77   6.623%   $216.1995   $216.20   $216.20   $216.20  
  Purchase #7 $42.31   5.689%   $44.717   $44.72   $44.70   $44.70  
  7 purchase totals = $1,107.91       $1,202.2628   $1,202.27   $1,202.30   $1,202.30