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 $186.89   11.701%   $208.758   $208.76   $208.75   $208.80  
  Purchase #2 $220.99   8.185%   $239.078   $239.08   $239.10   $239.10  
  Purchase #3 $242.73   8.610%   $263.6291   $263.63   $263.65   $263.60  
  Purchase #4 $60.35   8.796%   $65.6584   $65.66   $65.65   $65.70  
  Purchase #5 $34.78   6.190%   $36.9329   $36.93   $36.95   $36.90  
  Purchase #6 $244.61   7.869%   $263.8584   $263.86   $263.85   $263.90  
  Purchase #7 $41.92   6.743%   $44.7467   $44.75   $44.75   $44.70  
  7 purchase totals = $1,032.27       $1,122.6615   $1,122.67   $1,122.70   $1,122.70