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 $208.25   13.328%   $236.0056   $236.01   $236.00   $236.00  
  Purchase #2 $99.35   4.128%   $103.4512   $103.45   $103.45   $103.50  
  Purchase #3 $177.80   13.754%   $202.2546   $202.25   $202.25   $202.30  
  Purchase #4 $75.62   3.406%   $78.1956   $78.20   $78.20   $78.20  
  Purchase #5 $200.52   5.423%   $211.3942   $211.39   $211.40   $211.40  
  Purchase #6 $95.91   9.697%   $105.2104   $105.21   $105.20   $105.20  
  Purchase #7 $153.86   7.854%   $165.9442   $165.94   $165.95   $165.90  
  7 purchase totals = $1,011.31       $1,102.4558   $1,102.45   $1,102.45   $1,102.50