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 $144.63   5.358%   $152.3793   $152.38   $152.40   $152.40  
  Purchase #2 $166.66   11.705%   $186.1676   $186.17   $186.15   $186.20  
  Purchase #3 $151.43   8.680%   $164.5741   $164.57   $164.55   $164.60  
  Purchase #4 $171.96   5.610%   $181.607   $181.61   $181.60   $181.60  
  Purchase #5 $10.79   4.361%   $11.2606   $11.26   $11.25   $11.30  
  Purchase #6 $202.84   11.705%   $226.5824   $226.58   $226.60   $226.60  
  Purchase #7 $185.67   4.283%   $193.6222   $193.62   $193.60   $193.60  
  7 purchase totals = $1,033.98       $1,116.1932   $1,116.19   $1,116.15   $1,116.30