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 $105.46   8.109%   $114.0118   $114.01   $114.00   $114.00  
  Purchase #2 $98.49   11.357%   $109.6755   $109.68   $109.70   $109.70  
  Purchase #3 $240.89   9.262%   $263.2012   $263.20   $263.20   $263.20  
  Purchase #4 $55.37   3.276%   $57.1839   $57.18   $57.20   $57.20  
  Purchase #5 $185.35   11.213%   $206.1333   $206.13   $206.15   $206.10  
  Purchase #6 $77.83   9.320%   $85.0838   $85.08   $85.10   $85.10  
  Purchase #7 $180.91   5.451%   $190.7714   $190.77   $190.75   $190.80  
  7 purchase totals = $944.30       $1,026.0609   $1,026.05   $1,026.10   $1,026.10