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 $103.66   10.486%   $114.5298   $114.53   $114.55   $114.50  
  Purchase #2 $47.93   11.854%   $53.6116   $53.61   $53.60   $53.60  
  Purchase #3 $224.36   3.334%   $231.8402   $231.84   $231.85   $231.80  
  Purchase #4 $64.79   7.796%   $69.841   $69.84   $69.85   $69.80  
  Purchase #5 $95.52   13.570%   $108.4821   $108.48   $108.50   $108.50  
  Purchase #6 $177.41   8.374%   $192.2663   $192.27   $192.25   $192.30  
  Purchase #7 $165.37   10.551%   $182.8182   $182.82   $182.80   $182.80  
  7 purchase totals = $879.04       $953.3892   $953.39   $953.40   $953.30