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 $83.49   13.829%   $95.0358   $95.04   $95.05   $95.00  
  Purchase #2 $135.45   8.576%   $147.0662   $147.07   $147.05   $147.10  
  Purchase #3 $5.87   3.367%   $6.0676   $6.07   $6.05   $6.10  
  Purchase #4 $174.84   9.381%   $191.2417   $191.24   $191.25   $191.20  
  Purchase #5 $117.76   6.442%   $125.3461   $125.35   $125.35   $125.30  
  Purchase #6 $173.68   11.331%   $193.3597   $193.36   $193.35   $193.40  
  Purchase #7 $185.80   7.197%   $199.172   $199.17   $199.15   $199.20  
  7 purchase totals = $876.89       $957.2891   $957.30   $957.25   $957.30