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 $24.89   4.341%   $25.9705   $25.97   $25.95   $26.00  
  Purchase #2 $46.72   8.233%   $50.5665   $50.57   $50.55   $50.60  
  Purchase #3 $225.57   9.504%   $247.0082   $247.01   $247.00   $247.00  
  Purchase #4 $187.70   7.238%   $201.2857   $201.29   $201.30   $201.30  
  Purchase #5 $40.70   7.116%   $43.5962   $43.60   $43.60   $43.60  
  Purchase #6 $186.78   5.759%   $197.5367   $197.54   $197.55   $197.50  
  Purchase #7 $247.65   4.497%   $258.7868   $258.79   $258.80   $258.80  
  7 purchase totals = $960.01       $1,024.7506   $1,024.77   $1,024.75   $1,024.80