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 $46.97   10.629%   $51.9624   $51.96   $51.95   $52.00  
  Purchase #2 $209.63   10.371%   $231.3707   $231.37   $231.35   $231.40  
  Purchase #3 $53.65   4.407%   $56.0144   $56.01   $56.00   $56.00  
  Purchase #4 $181.75   13.472%   $206.2354   $206.24   $206.25   $206.20  
  Purchase #5 $216.76   8.177%   $234.4845   $234.48   $234.50   $234.50  
  Purchase #6 $164.81   5.866%   $174.4778   $174.48   $174.50   $174.50  
  Purchase #7 $218.99   7.613%   $235.6617   $235.66   $235.65   $235.70  
  7 purchase totals = $1,092.56       $1,190.2069   $1,190.20   $1,190.20   $1,190.30