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 $169.83   13.603%   $192.932   $192.93   $192.95   $192.90  
  Purchase #2 $38.87   9.838%   $42.694   $42.69   $42.70   $42.70  
  Purchase #3 $45.95   6.716%   $49.036   $49.04   $49.05   $49.00  
  Purchase #4 $243.35   7.631%   $261.92   $261.92   $261.90   $261.90  
  Purchase #5 $123.25   5.480%   $130.0041   $130.00   $130.00   $130.00  
  Purchase #6 $197.89   7.384%   $212.5022   $212.50   $212.50   $212.50  
  Purchase #7 $240.62   13.197%   $272.3746   $272.37   $272.35   $272.40  
  7 purchase totals = $1,059.76       $1,161.4629   $1,161.45   $1,161.45   $1,161.40