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 $95.44   11.493%   $106.4089   $106.41   $106.40   $106.40  
  Purchase #2 $211.26   13.413%   $239.5963   $239.60   $239.60   $239.60  
  Purchase #3 $42.39   5.714%   $44.8122   $44.81   $44.80   $44.80  
  Purchase #4 $178.42   13.168%   $201.9143   $201.91   $201.90   $201.90  
  Purchase #5 $67.55   8.874%   $73.5444   $73.54   $73.55   $73.50  
  Purchase #6 $243.33   6.438%   $258.9956   $259.00   $259.00   $259.00  
  Purchase #7 $94.47   13.858%   $107.5617   $107.56   $107.55   $107.60  
  7 purchase totals = $932.86       $1,032.8334   $1,032.83   $1,032.80   $1,032.80