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 $39.36   10.718%   $43.5786   $43.58   $43.60   $43.60  
  Purchase #2 $188.99   11.648%   $211.0036   $211.00   $211.00   $211.00  
  Purchase #3 $107.65   5.677%   $113.7613   $113.76   $113.75   $113.80  
  Purchase #4 $200.59   3.138%   $206.8845   $206.88   $206.90   $206.90  
  Purchase #5 $101.98   6.266%   $108.3701   $108.37   $108.35   $108.40  
  Purchase #6 $171.50   4.157%   $178.6293   $178.63   $178.65   $178.60  
  Purchase #7 $208.97   3.573%   $216.4365   $216.44   $216.45   $216.40  
  7 purchase totals = $1,019.04       $1,078.6639   $1,078.66   $1,078.70   $1,078.70