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 $62.54   13.538%   $71.0067   $71.01   $71.00   $71.00  
  Purchase #2 $101.28   13.183%   $114.6317   $114.63   $114.65   $114.60  
  Purchase #3 $97.30   12.123%   $109.0957   $109.10   $109.10   $109.10  
  Purchase #4 $202.61   3.426%   $209.5514   $209.55   $209.55   $209.60  
  Purchase #5 $221.96   6.458%   $236.2942   $236.29   $236.30   $236.30  
  Purchase #6 $128.41   11.301%   $142.9216   $142.92   $142.90   $142.90  
  Purchase #7 $73.89   7.215%   $79.2212   $79.22   $79.20   $79.20  
  7 purchase totals = $887.99       $962.7225   $962.72   $962.70   $962.70