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 $204.81   5.441%   $215.9537   $215.95   $215.95   $216.00  
  Purchase #2 $58.61   9.557%   $64.2114   $64.21   $64.20   $64.20  
  Purchase #3 $249.26   6.557%   $265.604   $265.60   $265.60   $265.60  
  Purchase #4 $188.76   4.430%   $197.1221   $197.12   $197.10   $197.10  
  Purchase #5 $212.26   4.704%   $222.2447   $222.24   $222.25   $222.20  
  Purchase #6 $31.36   12.769%   $35.3644   $35.36   $35.35   $35.40  
  Purchase #7 $20.88   3.193%   $21.5467   $21.55   $21.55   $21.50  
  7 purchase totals = $965.94       $1,022.0470   $1,022.03   $1,022.00   $1,022.00