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 $69.25   9.173%   $75.6023   $75.60   $75.60   $75.60  
  Purchase #2 $226.61   4.110%   $235.9237   $235.92   $235.90   $235.90  
  Purchase #3 $60.62   4.194%   $63.1624   $63.16   $63.15   $63.20  
  Purchase #4 $219.39   11.376%   $244.3478   $244.35   $244.35   $244.30  
  Purchase #5 $241.48   6.681%   $257.6133   $257.61   $257.60   $257.60  
  Purchase #6 $87.37   13.305%   $98.9946   $98.99   $99.00   $99.00  
  Purchase #7 $250.43   5.846%   $265.0701   $265.07   $265.05   $265.10  
  7 purchase totals = $1,155.15       $1,240.7142   $1,240.70   $1,240.65   $1,240.70