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 $177.68   11.127%   $197.4505   $197.45   $197.45   $197.50  
  Purchase #2 $138.39   9.610%   $151.6893   $151.69   $151.70   $151.70  
  Purchase #3 $213.56   3.678%   $221.4147   $221.41   $221.40   $221.40  
  Purchase #4 $228.99   6.656%   $244.2316   $244.23   $244.25   $244.20  
  Purchase #5 $66.51   8.241%   $71.9911   $71.99   $72.00   $72.00  
  Purchase #6 $181.89   6.295%   $193.34   $193.34   $193.35   $193.30  
  Purchase #7 $176.35   5.631%   $186.2803   $186.28   $186.30   $186.30  
  7 purchase totals = $1,183.37       $1,266.3975   $1,266.39   $1,266.45   $1,266.40