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 $205.62   10.444%   $227.095   $227.10   $227.10   $227.10  
  Purchase #2 $60.34   8.355%   $65.3814   $65.38   $65.40   $65.40  
  Purchase #3 $233.68   12.607%   $263.14   $263.14   $263.15   $263.10  
  Purchase #4 $241.80   13.140%   $273.5725   $273.57   $273.55   $273.60  
  Purchase #5 $132.79   11.636%   $148.2414   $148.24   $148.25   $148.20  
  Purchase #6 $185.56   4.493%   $193.8972   $193.90   $193.90   $193.90  
  Purchase #7 $189.41   4.662%   $198.2403   $198.24   $198.25   $198.20  
  7 purchase totals = $1,249.20       $1,369.5678   $1,369.57   $1,369.60   $1,369.50