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 $104.45   11.294%   $116.2466   $116.25   $116.25   $116.20  
  Purchase #2 $227.47   4.738%   $238.2475   $238.25   $238.25   $238.20  
  Purchase #3 $184.49   6.859%   $197.1442   $197.14   $197.15   $197.10  
  Purchase #4 $206.28   4.763%   $216.1051   $216.11   $216.10   $216.10  
  Purchase #5 $50.99   12.773%   $57.503   $57.50   $57.50   $57.50  
  Purchase #6 $243.36   7.661%   $262.0038   $262.00   $262.00   $262.00  
  Purchase #7 $7.59   9.397%   $8.3032   $8.30   $8.30   $8.30  
  7 purchase totals = $1,024.63       $1,095.5534   $1,095.55   $1,095.55   $1,095.40