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 $85.48   8.335%   $92.6048   $92.60   $92.60   $92.60  
  Purchase #2 $229.97   9.143%   $250.9962   $251.00   $251.00   $251.00  
  Purchase #3 $112.26   9.621%   $123.0605   $123.06   $123.05   $123.10  
  Purchase #4 $172.81   5.169%   $181.7425   $181.74   $181.75   $181.70  
  Purchase #5 $194.69   11.827%   $217.716   $217.72   $217.70   $217.70  
  Purchase #6 $105.56   13.422%   $119.7283   $119.73   $119.75   $119.70  
  Purchase #7 $65.62   6.564%   $69.9273   $69.93   $69.95   $69.90  
  7 purchase totals = $966.39       $1,055.7756   $1,055.78   $1,055.80   $1,055.70