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 $213.94   7.199%   $229.3415   $229.34   $229.35   $229.30  
  Purchase #2 $200.62   7.509%   $215.6846   $215.68   $215.70   $215.70  
  Purchase #3 $59.97   7.696%   $64.5853   $64.59   $64.60   $64.60  
  Purchase #4 $232.92   8.154%   $251.9123   $251.91   $251.90   $251.90  
  Purchase #5 $46.50   13.704%   $52.8724   $52.87   $52.85   $52.90  
  Purchase #6 $115.66   5.722%   $122.2781   $122.28   $122.30   $122.30  
  Purchase #7 $86.81   6.717%   $92.641   $92.64   $92.65   $92.60  
  7 purchase totals = $956.42       $1,029.3152   $1,029.31   $1,029.35   $1,029.30