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 $116.35   5.553%   $122.8109   $122.81   $122.80   $122.80  
  Purchase #2 $187.40   4.851%   $196.4908   $196.49   $196.50   $196.50  
  Purchase #3 $96.35   4.755%   $100.9314   $100.93   $100.95   $100.90  
  Purchase #4 $53.49   5.163%   $56.2517   $56.25   $56.25   $56.30  
  Purchase #5 $71.82   4.405%   $74.9837   $74.98   $75.00   $75.00  
  Purchase #6 $211.80   11.280%   $235.691   $235.69   $235.70   $235.70  
  Purchase #7 $97.70   8.802%   $106.2996   $106.30   $106.30   $106.30  
  7 purchase totals = $834.91       $893.4591   $893.45   $893.50   $893.50