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 $76.60   13.377%   $86.8468   $86.85   $86.85   $86.80  
  Purchase #2 $197.50   5.209%   $207.7878   $207.79   $207.80   $207.80  
  Purchase #3 $41.41   4.842%   $43.4151   $43.42   $43.40   $43.40  
  Purchase #4 $181.32   4.670%   $189.7876   $189.79   $189.80   $189.80  
  Purchase #5 $170.77   9.186%   $186.4569   $186.46   $186.45   $186.50  
  Purchase #6 $186.55   3.488%   $193.0569   $193.06   $193.05   $193.10  
  Purchase #7 $103.82   3.184%   $107.1256   $107.13   $107.15   $107.10  
  7 purchase totals = $957.97       $1,014.4767   $1,014.50   $1,014.50   $1,014.50