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 $48.98   9.403%   $53.5856   $53.59   $53.60   $53.60  
  Purchase #2 $223.85   8.201%   $242.2079   $242.21   $242.20   $242.20  
  Purchase #3 $247.41   6.731%   $264.0632   $264.06   $264.05   $264.10  
  Purchase #4 $77.62   11.418%   $86.4827   $86.48   $86.50   $86.50  
  Purchase #5 $206.89   13.861%   $235.567   $235.57   $235.55   $235.60  
  Purchase #6 $125.50   3.214%   $129.5336   $129.53   $129.55   $129.50  
  Purchase #7 $197.58   5.271%   $207.9944   $207.99   $208.00   $208.00  
  7 purchase totals = $1,127.83       $1,219.4344   $1,219.43   $1,219.45   $1,219.50