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 $60.58   12.159%   $67.9459   $67.95   $67.95   $67.90  
  Purchase #2 $156.66   4.585%   $163.8429   $163.84   $163.85   $163.80  
  Purchase #3 $104.68   8.647%   $113.7317   $113.73   $113.75   $113.70  
  Purchase #4 $120.84   6.659%   $128.8867   $128.89   $128.90   $128.90  
  Purchase #5 $160.25   5.858%   $169.6374   $169.64   $169.65   $169.60  
  Purchase #6 $216.88   6.682%   $231.3719   $231.37   $231.35   $231.40  
  Purchase #7 $234.61   11.653%   $261.9491   $261.95   $261.95   $261.90  
  7 purchase totals = $1,054.50       $1,137.3656   $1,137.37   $1,137.40   $1,137.20