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 $91.93   4.702%   $96.2525   $96.25   $96.25   $96.30  
  Purchase #2 $110.92   10.393%   $122.4479   $122.45   $122.45   $122.40  
  Purchase #3 $144.83   12.167%   $162.4515   $162.45   $162.45   $162.50  
  Purchase #4 $193.85   3.815%   $201.2454   $201.25   $201.25   $201.20  
  Purchase #5 $135.29   12.448%   $152.1309   $152.13   $152.15   $152.10  
  Purchase #6 $68.49   8.625%   $74.3973   $74.40   $74.40   $74.40  
  Purchase #7 $201.37   6.828%   $215.1195   $215.12   $215.10   $215.10  
  7 purchase totals = $946.68       $1,024.0450   $1,024.05   $1,024.05   $1,024.00