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 $70.28   5.868%   $74.404   $74.40   $74.40   $74.40  
  Purchase #2 $99.79   11.874%   $111.6391   $111.64   $111.65   $111.60  
  Purchase #3 $168.37   13.230%   $190.6454   $190.65   $190.65   $190.60  
  Purchase #4 $224.81   7.820%   $242.3901   $242.39   $242.40   $242.40  
  Purchase #5 $91.80   7.660%   $98.8319   $98.83   $98.85   $98.80  
  Purchase #6 $221.73   11.580%   $247.4063   $247.41   $247.40   $247.40  
  Purchase #7 $58.67   5.665%   $61.9937   $61.99   $62.00   $62.00  
  7 purchase totals = $935.45       $1,027.3105   $1,027.31   $1,027.35   $1,027.20