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 $43.99   9.195%   $48.0349   $48.03   $48.05   $48.00  
  Purchase #2 $227.71   5.356%   $239.9061   $239.91   $239.90   $239.90  
  Purchase #3 $129.38   9.388%   $141.5262   $141.53   $141.55   $141.50  
  Purchase #4 $72.81   6.668%   $77.665   $77.67   $77.65   $77.70  
  Purchase #5 $104.37   6.427%   $111.0779   $111.08   $111.10   $111.10  
  Purchase #6 $23.91   10.353%   $26.3854   $26.39   $26.40   $26.40  
  Purchase #7 $73.42   9.244%   $80.2069   $80.21   $80.20   $80.20  
  7 purchase totals = $675.59       $724.8024   $724.82   $724.85   $724.80