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 $191.53   8.510%   $207.8292   $207.83   $207.85   $207.80  
  Purchase #2 $87.42   12.162%   $98.052   $98.05   $98.05   $98.10  
  Purchase #3 $178.25   8.245%   $192.9467   $192.95   $192.95   $192.90  
  Purchase #4 $62.26   4.744%   $65.2136   $65.21   $65.20   $65.20  
  Purchase #5 $89.26   12.494%   $100.4121   $100.41   $100.40   $100.40  
  Purchase #6 $228.53   12.868%   $257.9372   $257.94   $257.95   $257.90  
  Purchase #7 $85.92   10.186%   $94.6718   $94.67   $94.65   $94.70  
  7 purchase totals = $923.17       $1,017.0626   $1,017.06   $1,017.05   $1,017.00