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 $186.44   11.630%   $208.123   $208.12   $208.10   $208.10  
  Purchase #2 $111.81   13.271%   $126.6483   $126.65   $126.65   $126.60  
  Purchase #3 $132.73   11.202%   $147.5984   $147.60   $147.60   $147.60  
  Purchase #4 $154.25   11.148%   $171.4458   $171.45   $171.45   $171.40  
  Purchase #5 $47.40   9.866%   $52.0765   $52.08   $52.10   $52.10  
  Purchase #6 $192.69   8.864%   $209.77   $209.77   $209.75   $209.80  
  Purchase #7 $103.56   4.206%   $107.9157   $107.92   $107.90   $107.90  
  7 purchase totals = $928.88       $1,023.5777   $1,023.59   $1,023.55   $1,023.50