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 $183.30   10.186%   $201.9709   $201.97   $201.95   $202.00  
  Purchase #2 $146.87   8.403%   $159.2115   $159.21   $159.20   $159.20  
  Purchase #3 $78.87   9.723%   $86.5385   $86.54   $86.55   $86.50  
  Purchase #4 $125.90   5.273%   $132.5387   $132.54   $132.55   $132.50  
  Purchase #5 $38.66   11.336%   $43.0425   $43.04   $43.05   $43.00  
  Purchase #6 $171.90   3.610%   $178.1056   $178.11   $178.10   $178.10  
  Purchase #7 $191.56   13.620%   $217.6505   $217.65   $217.65   $217.70  
  7 purchase totals = $937.06       $1,019.0582   $1,019.06   $1,019.05   $1,019.00