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 $145.95   4.795%   $152.9483   $152.95   $152.95   $152.90  
  Purchase #2 $86.46   13.640%   $98.2531   $98.25   $98.25   $98.30  
  Purchase #3 $153.87   3.250%   $158.8708   $158.87   $158.85   $158.90  
  Purchase #4 $62.93   7.780%   $67.826   $67.83   $67.85   $67.80  
  Purchase #5 $214.84   11.712%   $240.0021   $240.00   $240.00   $240.00  
  Purchase #6 $224.36   12.692%   $252.8358   $252.84   $252.85   $252.80  
  Purchase #7 $50.47   10.792%   $55.9167   $55.92   $55.90   $55.90  
  7 purchase totals = $938.88       $1,026.6528   $1,026.66   $1,026.65   $1,026.60