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 $34.47   5.212%   $36.2666   $36.27   $36.25   $36.30  
  Purchase #2 $184.83   6.327%   $196.5242   $196.52   $196.50   $196.50  
  Purchase #3 $63.36   3.699%   $65.7037   $65.70   $65.70   $65.70  
  Purchase #4 $202.46   7.591%   $217.8287   $217.83   $217.85   $217.80  
  Purchase #5 $168.53   8.252%   $182.4371   $182.44   $182.45   $182.40  
  Purchase #6 $235.51   5.631%   $248.7716   $248.77   $248.75   $248.80  
  Purchase #7 $87.64   10.209%   $96.5872   $96.59   $96.60   $96.60  
  7 purchase totals = $976.80       $1,044.1191   $1,044.12   $1,044.10   $1,044.10