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 $54.40   13.725%   $61.8664   $61.87   $61.85   $61.90  
  Purchase #2 $176.84   9.503%   $193.6451   $193.65   $193.65   $193.60  
  Purchase #3 $31.44   12.852%   $35.4807   $35.48   $35.50   $35.50  
  Purchase #4 $248.39   6.346%   $264.1528   $264.15   $264.15   $264.20  
  Purchase #5 $237.68   13.682%   $270.1994   $270.20   $270.20   $270.20  
  Purchase #6 $24.38   8.774%   $26.5191   $26.52   $26.50   $26.50  
  Purchase #7 $233.27   8.813%   $253.8281   $253.83   $253.85   $253.80  
  7 purchase totals = $1,006.40       $1,105.6916   $1,105.70   $1,105.70   $1,105.70