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 $95.52   6.527%   $101.7546   $101.75   $101.75   $101.80  
  Purchase #2 $224.60   4.655%   $235.0551   $235.06   $235.05   $235.10  
  Purchase #3 $185.46   8.581%   $201.3743   $201.37   $201.35   $201.40  
  Purchase #4 $113.36   8.355%   $122.8312   $122.83   $122.85   $122.80  
  Purchase #5 $191.44   12.478%   $215.3279   $215.33   $215.35   $215.30  
  Purchase #6 $197.93   8.597%   $214.946   $214.95   $214.95   $214.90  
  Purchase #7 $172.27   7.609%   $185.378   $185.38   $185.40   $185.40  
  7 purchase totals = $1,180.58       $1,276.6671   $1,276.67   $1,276.70   $1,276.70