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 $216.89   9.591%   $237.6919   $237.69   $237.70   $237.70  
  Purchase #2 $97.51   8.381%   $105.6823   $105.68   $105.70   $105.70  
  Purchase #3 $107.55   13.843%   $122.4381   $122.44   $122.45   $122.40  
  Purchase #4 $187.47   3.233%   $193.5309   $193.53   $193.55   $193.50  
  Purchase #5 $167.70   11.574%   $187.1096   $187.11   $187.10   $187.10  
  Purchase #6 $231.40   9.543%   $253.4825   $253.48   $253.50   $253.50  
  Purchase #7 $183.79   10.331%   $202.7773   $202.78   $202.80   $202.80  
  7 purchase totals = $1,192.31       $1,302.7126   $1,302.71   $1,302.80   $1,302.70