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 $208.35   11.355%   $232.0081   $232.01   $232.00   $232.00  
  Purchase #2 $151.74   13.115%   $171.6407   $171.64   $171.65   $171.60  
  Purchase #3 $210.28   6.713%   $224.3961   $224.40   $224.40   $224.40  
  Purchase #4 $98.88   9.209%   $107.9859   $107.99   $108.00   $108.00  
  Purchase #5 $84.49   10.367%   $93.2491   $93.25   $93.25   $93.20  
  Purchase #6 $146.81   12.711%   $165.471   $165.47   $165.45   $165.50  
  Purchase #7 $92.55   10.420%   $102.1937   $102.19   $102.20   $102.20  
  7 purchase totals = $993.10       $1,096.9446   $1,096.95   $1,096.95   $1,096.90