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 $84.26   13.385%   $95.5382   $95.54   $95.55   $95.50  
  Purchase #2 $147.96   12.368%   $166.2597   $166.26   $166.25   $166.30  
  Purchase #3 $239.58   7.658%   $257.927   $257.93   $257.95   $257.90  
  Purchase #4 $113.52   7.145%   $121.631   $121.63   $121.65   $121.60  
  Purchase #5 $250.83   9.223%   $273.9641   $273.96   $273.95   $274.00  
  Purchase #6 $241.92   4.235%   $252.1653   $252.17   $252.15   $252.20  
  Purchase #7 $70.81   10.504%   $78.2479   $78.25   $78.25   $78.20  
  7 purchase totals = $1,148.88       $1,245.7332   $1,245.74   $1,245.75   $1,245.70