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 $186.74   7.611%   $200.9528   $200.95   $200.95   $201.00  
  Purchase #2 $166.54   6.748%   $177.7781   $177.78   $177.80   $177.80  
  Purchase #3 $164.53   6.735%   $175.6111   $175.61   $175.60   $175.60  
  Purchase #4 $136.93   12.532%   $154.0901   $154.09   $154.10   $154.10  
  Purchase #5 $204.76   3.131%   $211.171   $211.17   $211.15   $211.20  
  Purchase #6 $158.30   6.414%   $168.4534   $168.45   $168.45   $168.50  
  Purchase #7 $243.59   13.656%   $276.8547   $276.85   $276.85   $276.90  
  7 purchase totals = $1,261.39       $1,364.9112   $1,364.90   $1,364.90   $1,365.10