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 $64.44   6.505%   $68.6318   $68.63   $68.65   $68.60  
  Purchase #2 $247.59   6.244%   $263.0495   $263.05   $263.05   $263.00  
  Purchase #3 $52.40   4.105%   $54.551   $54.55   $54.55   $54.60  
  Purchase #4 $147.76   6.726%   $157.6983   $157.70   $157.70   $157.70  
  Purchase #5 $176.26   5.569%   $186.0759   $186.08   $186.10   $186.10  
  Purchase #6 $176.57   9.582%   $193.4889   $193.49   $193.50   $193.50  
  Purchase #7 $187.89   8.231%   $203.3552   $203.36   $203.35   $203.40  
  7 purchase totals = $1,052.91       $1,126.8506   $1,126.86   $1,126.90   $1,126.90