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 $208.72   11.161%   $232.0152   $232.02   $232.00   $232.00  
  Purchase #2 $37.99   3.292%   $39.2406   $39.24   $39.25   $39.20  
  Purchase #3 $41.42   7.337%   $44.459   $44.46   $44.45   $44.50  
  Purchase #4 $150.39   7.868%   $162.2227   $162.22   $162.20   $162.20  
  Purchase #5 $214.34   8.809%   $233.2212   $233.22   $233.20   $233.20  
  Purchase #6 $168.41   12.749%   $189.8806   $189.88   $189.90   $189.90  
  Purchase #7 $110.40   12.667%   $124.3844   $124.38   $124.40   $124.40  
  7 purchase totals = $931.67       $1,025.4237   $1,025.42   $1,025.40   $1,025.40