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 $65.29   7.119%   $69.938   $69.94   $69.95   $69.90  
  Purchase #2 $104.44   9.136%   $113.9816   $113.98   $114.00   $114.00  
  Purchase #3 $177.68   8.853%   $193.41   $193.41   $193.40   $193.40  
  Purchase #4 $14.83   11.687%   $16.5632   $16.56   $16.55   $16.60  
  Purchase #5 $166.68   13.458%   $189.1118   $189.11   $189.10   $189.10  
  Purchase #6 $219.44   6.803%   $234.3685   $234.37   $234.35   $234.40  
  Purchase #7 $224.41   6.632%   $239.2929   $239.29   $239.30   $239.30  
  7 purchase totals = $972.77       $1,056.6660   $1,056.66   $1,056.65   $1,056.70