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 $182.73   8.241%   $197.7888   $197.79   $197.80   $197.80  
  Purchase #2 $235.90   10.511%   $260.6954   $260.70   $260.70   $260.70  
  Purchase #3 $232.34   13.623%   $263.9917   $263.99   $264.00   $264.00  
  Purchase #4 $49.77   8.317%   $53.9094   $53.91   $53.90   $53.90  
  Purchase #5 $59.27   11.437%   $66.0487   $66.05   $66.05   $66.00  
  Purchase #6 $193.65   7.700%   $208.5611   $208.56   $208.55   $208.60  
  Purchase #7 $52.97   11.859%   $59.2517   $59.25   $59.25   $59.30  
  7 purchase totals = $1,006.63       $1,110.2468   $1,110.25   $1,110.25   $1,110.30