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 $88.77   4.239%   $92.533   $92.53   $92.55   $92.50  
  Purchase #2 $43.26   3.271%   $44.675   $44.68   $44.70   $44.70  
  Purchase #3 $159.81   10.857%   $177.1606   $177.16   $177.15   $177.20  
  Purchase #4 $202.31   3.153%   $208.6888   $208.69   $208.70   $208.70  
  Purchase #5 $102.64   6.772%   $109.5908   $109.59   $109.60   $109.60  
  Purchase #6 $68.48   9.147%   $74.7439   $74.74   $74.75   $74.70  
  Purchase #7 $211.55   3.377%   $218.694   $218.69   $218.70   $218.70  
  7 purchase totals = $876.82       $926.0861   $926.08   $926.15   $926.10