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 $217.67   7.844%   $234.744   $234.74   $234.75   $234.70  
  Purchase #2 $206.57   13.699%   $234.868   $234.87   $234.85   $234.90  
  Purchase #3 $212.86   9.162%   $232.3622   $232.36   $232.35   $232.40  
  Purchase #4 $100.85   6.596%   $107.5021   $107.50   $107.50   $107.50  
  Purchase #5 $86.45   6.508%   $92.0762   $92.08   $92.10   $92.10  
  Purchase #6 $119.78   4.262%   $124.885   $124.89   $124.90   $124.90  
  Purchase #7 $81.41   10.804%   $90.2055   $90.21   $90.20   $90.20  
  7 purchase totals = $1,025.59       $1,116.6430   $1,116.65   $1,116.65   $1,116.70