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 $59.88   8.655%   $65.0626   $65.06   $65.05   $65.10  
  Purchase #2 $157.87   8.727%   $171.6473   $171.65   $171.65   $171.60  
  Purchase #3 $210.31   7.653%   $226.405   $226.41   $226.40   $226.40  
  Purchase #4 $65.67   13.200%   $74.3384   $74.34   $74.35   $74.30  
  Purchase #5 $226.51   3.726%   $234.9498   $234.95   $234.95   $234.90  
  Purchase #6 $239.49   11.275%   $266.4925   $266.49   $266.50   $266.50  
  Purchase #7 $67.85   9.550%   $74.3297   $74.33   $74.35   $74.30  
  7 purchase totals = $1,027.58       $1,113.2253   $1,113.23   $1,113.25   $1,113.10