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 $75.70   13.623%   $86.0126   $86.01   $86.00   $86.00  
  Purchase #2 $174.98   6.533%   $186.4114   $186.41   $186.40   $186.40  
  Purchase #3 $183.97   6.294%   $195.5491   $195.55   $195.55   $195.50  
  Purchase #4 $61.32   4.135%   $63.8556   $63.86   $63.85   $63.90  
  Purchase #5 $13.41   10.124%   $14.7676   $14.77   $14.75   $14.80  
  Purchase #6 $233.88   9.802%   $256.8049   $256.80   $256.80   $256.80  
  Purchase #7 $196.49   11.338%   $218.768   $218.77   $218.75   $218.80  
  7 purchase totals = $939.75       $1,022.1692   $1,022.17   $1,022.10   $1,022.20