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 $89.47   6.334%   $95.137   $95.14   $95.15   $95.10  
  Purchase #2 $234.47   9.126%   $255.8677   $255.87   $255.85   $255.90  
  Purchase #3 $35.98   8.838%   $39.1599   $39.16   $39.15   $39.20  
  Purchase #4 $112.48   4.324%   $117.3436   $117.34   $117.35   $117.30  
  Purchase #5 $148.87   13.836%   $169.4677   $169.47   $169.45   $169.50  
  Purchase #6 $239.56   9.369%   $262.0044   $262.00   $262.00   $262.00  
  Purchase #7 $114.65   5.225%   $120.6405   $120.64   $120.65   $120.60  
  7 purchase totals = $975.48       $1,059.6208   $1,059.62   $1,059.60   $1,059.60