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 $212.65   13.318%   $240.9707   $240.97   $240.95   $241.00  
  Purchase #2 $62.76   8.475%   $68.0789   $68.08   $68.10   $68.10  
  Purchase #3 $100.32   12.701%   $113.0616   $113.06   $113.05   $113.10  
  Purchase #4 $100.41   13.523%   $113.9884   $113.99   $114.00   $114.00  
  Purchase #5 $215.65   12.294%   $242.162   $242.16   $242.15   $242.20  
  Purchase #6 $53.29   12.757%   $60.0882   $60.09   $60.10   $60.10  
  Purchase #7 $220.47   8.149%   $238.4361   $238.44   $238.45   $238.40  
  7 purchase totals = $965.55       $1,076.7859   $1,076.79   $1,076.80   $1,076.90