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 $189.85   8.113%   $205.2525   $205.25   $205.25   $205.30  
  Purchase #2 $32.99   5.126%   $34.6811   $34.68   $34.70   $34.70  
  Purchase #3 $27.66   9.769%   $30.3621   $30.36   $30.35   $30.40  
  Purchase #4 $242.60   9.341%   $265.2613   $265.26   $265.25   $265.30  
  Purchase #5 $188.54   6.789%   $201.34   $201.34   $201.35   $201.30  
  Purchase #6 $163.43   4.771%   $171.2272   $171.23   $171.25   $171.20  
  Purchase #7 $188.31   3.412%   $194.7351   $194.74   $194.75   $194.70  
  7 purchase totals = $1,033.38       $1,102.8593   $1,102.86   $1,102.90   $1,102.90