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 $242.79   10.796%   $269.0016   $269.00   $269.00   $269.00  
  Purchase #2 $213.41   10.309%   $235.4104   $235.41   $235.40   $235.40  
  Purchase #3 $52.89   6.769%   $56.4701   $56.47   $56.45   $56.50  
  Purchase #4 $210.96   13.796%   $240.064   $240.06   $240.05   $240.10  
  Purchase #5 $177.74   8.369%   $192.6151   $192.62   $192.60   $192.60  
  Purchase #6 $46.54   9.370%   $50.9008   $50.90   $50.90   $50.90  
  Purchase #7 $23.45   5.817%   $24.8141   $24.81   $24.80   $24.80  
  7 purchase totals = $967.78       $1,069.2761   $1,069.27   $1,069.20   $1,069.30