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 $59.58   13.403%   $67.5655   $67.57   $67.55   $67.60  
  Purchase #2 $127.26   7.467%   $136.7625   $136.76   $136.75   $136.80  
  Purchase #3 $238.89   5.498%   $252.0242   $252.02   $252.00   $252.00  
  Purchase #4 $93.73   3.715%   $97.2121   $97.21   $97.20   $97.20  
  Purchase #5 $239.74   7.520%   $257.7684   $257.77   $257.75   $257.80  
  Purchase #6 $202.72   7.502%   $217.9281   $217.93   $217.95   $217.90  
  Purchase #7 $74.60   3.723%   $77.3774   $77.38   $77.40   $77.40  
  7 purchase totals = $1,036.52       $1,106.6382   $1,106.64   $1,106.60   $1,106.70