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 $182.91   7.202%   $196.0832   $196.08   $196.10   $196.10  
  Purchase #2 $61.41   6.328%   $65.296   $65.30   $65.30   $65.30  
  Purchase #3 $13.61   5.732%   $14.3901   $14.39   $14.40   $14.40  
  Purchase #4 $204.90   3.781%   $212.6473   $212.65   $212.65   $212.60  
  Purchase #5 $182.99   5.257%   $192.6098   $192.61   $192.60   $192.60  
  Purchase #6 $95.75   13.297%   $108.4819   $108.48   $108.50   $108.50  
  Purchase #7 $114.63   5.618%   $121.0699   $121.07   $121.05   $121.10  
  7 purchase totals = $856.20       $910.5782   $910.58   $910.60   $910.60