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 $206.97   4.871%   $217.0515   $217.05   $217.05   $217.10  
  Purchase #2 $33.65   4.565%   $35.1861   $35.19   $35.20   $35.20  
  Purchase #3 $200.96   11.354%   $223.777   $223.78   $223.80   $223.80  
  Purchase #4 $217.76   11.737%   $243.3185   $243.32   $243.30   $243.30  
  Purchase #5 $123.97   13.359%   $140.5312   $140.53   $140.55   $140.50  
  Purchase #6 $245.93   8.253%   $266.2266   $266.23   $266.25   $266.20  
  Purchase #7 $182.84   9.504%   $200.2171   $200.22   $200.20   $200.20  
  7 purchase totals = $1,212.08       $1,326.3080   $1,326.32   $1,326.35   $1,326.30