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 $67.49   12.509%   $75.9323   $75.93   $75.95   $75.90  
  Purchase #2 $185.25   8.313%   $200.6498   $200.65   $200.65   $200.60  
  Purchase #3 $231.88   6.805%   $247.6594   $247.66   $247.65   $247.70  
  Purchase #4 $61.68   10.670%   $68.2613   $68.26   $68.25   $68.30  
  Purchase #5 $122.79   3.697%   $127.3295   $127.33   $127.35   $127.30  
  Purchase #6 $190.38   11.654%   $212.5669   $212.57   $212.55   $212.60  
  Purchase #7 $221.90   10.669%   $245.5745   $245.57   $245.55   $245.60  
  7 purchase totals = $1,081.37       $1,177.9737   $1,177.97   $1,177.95   $1,178.00