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 $154.99   13.704%   $176.2298   $176.23   $176.25   $176.20  
  Purchase #2 $188.56   12.695%   $212.4977   $212.50   $212.50   $212.50  
  Purchase #3 $119.52   11.393%   $133.1369   $133.14   $133.15   $133.10  
  Purchase #4 $12.65   3.465%   $13.0883   $13.09   $13.10   $13.10  
  Purchase #5 $247.69   6.237%   $263.1384   $263.14   $263.15   $263.10  
  Purchase #6 $7.27   12.645%   $8.1893   $8.19   $8.20   $8.20  
  Purchase #7 $193.74   7.586%   $208.4371   $208.44   $208.45   $208.40  
  7 purchase totals = $924.42       $1,014.7175   $1,014.73   $1,014.80   $1,014.60