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 $216.90   11.213%   $241.221   $241.22   $241.20   $241.20  
  Purchase #2 $74.57   4.257%   $77.7444   $77.74   $77.75   $77.70  
  Purchase #3 $10.53   3.475%   $10.8959   $10.90   $10.90   $10.90  
  Purchase #4 $12.99   3.432%   $13.4358   $13.44   $13.45   $13.40  
  Purchase #5 $184.44   7.619%   $198.4925   $198.49   $198.50   $198.50  
  Purchase #6 $142.34   13.294%   $161.2627   $161.26   $161.25   $161.30  
  Purchase #7 $112.91   8.572%   $122.5886   $122.59   $122.60   $122.60  
  7 purchase totals = $754.68       $825.6409   $825.64   $825.65   $825.60