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 $23.25   11.730%   $25.9772   $25.98   $26.00   $26.00  
  Purchase #2 $95.47   8.482%   $103.5678   $103.57   $103.55   $103.60  
  Purchase #3 $79.44   6.574%   $84.6624   $84.66   $84.65   $84.70  
  Purchase #4 $104.94   4.794%   $109.9708   $109.97   $109.95   $110.00  
  Purchase #5 $169.84   3.527%   $175.8303   $175.83   $175.85   $175.80  
  Purchase #6 $190.74   11.345%   $212.3795   $212.38   $212.40   $212.40  
  Purchase #7 $57.61   3.463%   $59.605   $59.61   $59.60   $59.60  
  7 purchase totals = $721.29       $771.9930   $772.00   $772.00   $772.10