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 $61.25   10.291%   $67.5532   $67.55   $67.55   $67.60  
  Purchase #2 $208.84   7.133%   $223.7366   $223.74   $223.75   $223.70  
  Purchase #3 $122.76   9.815%   $134.8089   $134.81   $134.80   $134.80  
  Purchase #4 $101.89   5.391%   $107.3829   $107.38   $107.40   $107.40  
  Purchase #5 $110.57   4.272%   $115.2936   $115.29   $115.30   $115.30  
  Purchase #6 $236.33   13.125%   $267.3483   $267.35   $267.35   $267.30  
  Purchase #7 $238.69   3.469%   $246.9702   $246.97   $246.95   $247.00  
  7 purchase totals = $1,080.33       $1,163.0937   $1,163.09   $1,163.10   $1,163.10