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 $192.92   8.163%   $208.6681   $208.67   $208.65   $208.70  
  Purchase #2 $244.50   9.175%   $266.9329   $266.93   $266.95   $266.90  
  Purchase #3 $56.26   7.188%   $60.304   $60.30   $60.30   $60.30  
  Purchase #4 $116.78   13.247%   $132.2498   $132.25   $132.25   $132.20  
  Purchase #5 $187.97   4.629%   $196.6711   $196.67   $196.65   $196.70  
  Purchase #6 $97.39   11.395%   $108.4876   $108.49   $108.50   $108.50  
  Purchase #7 $39.84   4.300%   $41.5531   $41.55   $41.55   $41.60  
  7 purchase totals = $935.66       $1,014.8666   $1,014.86   $1,014.85   $1,014.90