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 $24.85   4.747%   $26.0296   $26.03   $26.05   $26.00  
  Purchase #2 $194.89   5.408%   $205.4297   $205.43   $205.45   $205.40  
  Purchase #3 $243.29   5.666%   $257.0748   $257.07   $257.05   $257.10  
  Purchase #4 $239.42   10.242%   $263.9414   $263.94   $263.95   $263.90  
  Purchase #5 $68.61   12.629%   $77.2748   $77.27   $77.25   $77.30  
  Purchase #6 $190.68   5.723%   $201.5926   $201.59   $201.60   $201.60  
  Purchase #7 $107.99   11.754%   $120.6831   $120.68   $120.70   $120.70  
  7 purchase totals = $1,069.73       $1,152.0260   $1,152.01   $1,152.05   $1,152.00