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 $176.69   4.493%   $184.6287   $184.63   $184.65   $184.60  
  Purchase #2 $27.58   11.273%   $30.6891   $30.69   $30.70   $30.70  
  Purchase #3 $195.56   7.175%   $209.5914   $209.59   $209.60   $209.60  
  Purchase #4 $160.94   6.621%   $171.5958   $171.60   $171.60   $171.60  
  Purchase #5 $230.90   11.629%   $257.7514   $257.75   $257.75   $257.80  
  Purchase #6 $96.92   4.833%   $101.6041   $101.60   $101.60   $101.60  
  Purchase #7 $63.64   8.454%   $69.0201   $69.02   $69.00   $69.00  
  7 purchase totals = $952.23       $1,024.8806   $1,024.88   $1,024.90   $1,024.90