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 $168.59   4.814%   $176.7059   $176.71   $176.70   $176.70  
  Purchase #2 $147.89   11.416%   $164.7731   $164.77   $164.75   $164.80  
  Purchase #3 $14.71   11.656%   $16.4246   $16.42   $16.40   $16.40  
  Purchase #4 $211.91   10.827%   $234.8535   $234.85   $234.85   $234.90  
  Purchase #5 $237.49   12.247%   $266.5754   $266.58   $266.60   $266.60  
  Purchase #6 $221.25   10.463%   $244.3994   $244.40   $244.40   $244.40  
  Purchase #7 $239.72   7.550%   $257.8189   $257.82   $257.80   $257.80  
  7 purchase totals = $1,241.56       $1,361.5508   $1,361.55   $1,361.50   $1,361.60