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 $142.85   13.437%   $162.0448   $162.04   $162.05   $162.00  
  Purchase #2 $174.31   7.193%   $186.8481   $186.85   $186.85   $186.80  
  Purchase #3 $92.77   4.795%   $97.2183   $97.22   $97.20   $97.20  
  Purchase #4 $86.41   11.559%   $96.3981   $96.40   $96.40   $96.40  
  Purchase #5 $115.99   5.253%   $122.083   $122.08   $122.10   $122.10  
  Purchase #6 $48.41   3.702%   $50.2021   $50.20   $50.20   $50.20  
  Purchase #7 $226.74   10.501%   $250.55   $250.55   $250.55   $250.60  
  7 purchase totals = $887.48       $965.3444   $965.34   $965.35   $965.30