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 $23.46   6.354%   $24.9506   $24.95   $24.95   $25.00  
  Purchase #2 $246.67   7.457%   $265.0642   $265.06   $265.05   $265.10  
  Purchase #3 $79.36   4.196%   $82.6899   $82.69   $82.70   $82.70  
  Purchase #4 $168.61   8.494%   $182.9317   $182.93   $182.95   $182.90  
  Purchase #5 $234.83   6.533%   $250.1714   $250.17   $250.15   $250.20  
  Purchase #6 $104.64   13.113%   $118.3614   $118.36   $118.35   $118.40  
  Purchase #7 $135.56   11.244%   $150.8024   $150.80   $150.80   $150.80  
  7 purchase totals = $993.13       $1,074.9716   $1,074.96   $1,074.95   $1,075.10