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 $197.39   4.181%   $205.6429   $205.64   $205.65   $205.60  
  Purchase #2 $77.42   11.158%   $86.0585   $86.06   $86.05   $86.10  
  Purchase #3 $216.74   4.109%   $225.6458   $225.65   $225.65   $225.60  
  Purchase #4 $233.37   3.284%   $241.0339   $241.03   $241.05   $241.00  
  Purchase #5 $107.80   13.219%   $122.0501   $122.05   $122.05   $122.10  
  Purchase #6 $215.80   4.752%   $226.0548   $226.05   $226.05   $226.10  
  Purchase #7 $73.95   13.841%   $84.1854   $84.19   $84.20   $84.20  
  7 purchase totals = $1,122.47       $1,190.6714   $1,190.67   $1,190.70   $1,190.70