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 $208.39   13.555%   $236.6373   $236.64   $236.65   $236.60  
  Purchase #2 $168.50   10.335%   $185.9145   $185.91   $185.90   $185.90  
  Purchase #3 $34.88   5.450%   $36.781   $36.78   $36.80   $36.80  
  Purchase #4 $180.30   12.616%   $203.0466   $203.05   $203.05   $203.00  
  Purchase #5 $97.46   7.758%   $105.0209   $105.02   $105.00   $105.00  
  Purchase #6 $64.63   5.817%   $68.3895   $68.39   $68.40   $68.40  
  Purchase #7 $203.72   13.818%   $231.87   $231.87   $231.85   $231.90  
  7 purchase totals = $957.88       $1,067.6598   $1,067.66   $1,067.65   $1,067.60