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 $65.75   13.525%   $74.6427   $74.64   $74.65   $74.60  
  Purchase #2 $167.61   4.577%   $175.2815   $175.28   $175.30   $175.30  
  Purchase #3 $75.43   12.432%   $84.8075   $84.81   $84.80   $84.80  
  Purchase #4 $183.89   10.335%   $202.895   $202.90   $202.90   $202.90  
  Purchase #5 $88.92   6.379%   $94.5922   $94.59   $94.60   $94.60  
  Purchase #6 $147.35   4.255%   $153.6197   $153.62   $153.60   $153.60  
  Purchase #7 $237.83   9.390%   $260.1622   $260.16   $260.15   $260.20  
  7 purchase totals = $966.78       $1,046.0008   $1,046.00   $1,046.00   $1,046.00