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 $57.79   7.217%   $61.9607   $61.96   $61.95   $62.00  
  Purchase #2 $229.90   4.563%   $240.3903   $240.39   $240.40   $240.40  
  Purchase #3 $201.75   3.396%   $208.6014   $208.60   $208.60   $208.60  
  Purchase #4 $60.80   3.825%   $63.1256   $63.13   $63.15   $63.10  
  Purchase #5 $191.99   8.471%   $208.2535   $208.25   $208.25   $208.30  
  Purchase #6 $174.33   3.177%   $179.8685   $179.87   $179.85   $179.90  
  Purchase #7 $243.94   3.243%   $251.851   $251.85   $251.85   $251.90  
  7 purchase totals = $1,160.50       $1,214.0510   $1,214.05   $1,214.05   $1,214.20