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 $84.81   12.731%   $95.6072   $95.61   $95.60   $95.60  
  Purchase #2 $217.44   9.604%   $238.3229   $238.32   $238.30   $238.30  
  Purchase #3 $130.83   9.158%   $142.8114   $142.81   $142.80   $142.80  
  Purchase #4 $199.44   9.783%   $218.9512   $218.95   $218.95   $219.00  
  Purchase #5 $108.32   8.102%   $117.0961   $117.10   $117.10   $117.10  
  Purchase #6 $10.65   12.636%   $11.9957   $12.00   $12.00   $12.00  
  Purchase #7 $44.59   10.524%   $49.2827   $49.28   $49.30   $49.30  
  7 purchase totals = $796.08       $874.0672   $874.07   $874.05   $874.10