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 $195.63   4.781%   $204.9831   $204.98   $205.00   $205.00  
  Purchase #2 $24.76   9.369%   $27.0798   $27.08   $27.10   $27.10  
  Purchase #3 $184.93   11.635%   $206.4466   $206.45   $206.45   $206.40  
  Purchase #4 $207.95   5.102%   $218.5596   $218.56   $218.55   $218.60  
  Purchase #5 $143.41   7.225%   $153.7714   $153.77   $153.75   $153.80  
  Purchase #6 $191.51   8.595%   $207.9703   $207.97   $207.95   $208.00  
  Purchase #7 $33.54   4.758%   $35.1358   $35.14   $35.15   $35.10  
  7 purchase totals = $981.73       $1,053.9466   $1,053.95   $1,053.95   $1,054.00