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 $208.61   13.635%   $237.054   $237.05   $237.05   $237.10  
  Purchase #2 $129.59   7.511%   $139.3235   $139.32   $139.30   $139.30  
  Purchase #3 $26.74   13.364%   $30.3135   $30.31   $30.30   $30.30  
  Purchase #4 $194.39   6.461%   $206.9495   $206.95   $206.95   $206.90  
  Purchase #5 $82.88   4.306%   $86.4488   $86.45   $86.45   $86.40  
  Purchase #6 $226.72   3.679%   $235.061   $235.06   $235.05   $235.10  
  Purchase #7 $240.53   9.700%   $263.8614   $263.86   $263.85   $263.90  
  7 purchase totals = $1,109.46       $1,199.0117   $1,199.00   $1,198.95   $1,199.00