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 $144.43   6.739%   $154.1631   $154.16   $154.15   $154.20  
  Purchase #2 $187.57   5.376%   $197.6538   $197.65   $197.65   $197.70  
  Purchase #3 $214.38   5.491%   $226.1516   $226.15   $226.15   $226.20  
  Purchase #4 $78.92   4.776%   $82.6892   $82.69   $82.70   $82.70  
  Purchase #5 $230.75   3.357%   $238.4963   $238.50   $238.50   $238.50  
  Purchase #6 $228.59   4.160%   $238.0993   $238.10   $238.10   $238.10  
  Purchase #7 $24.85   4.326%   $25.925   $25.93   $25.95   $25.90  
  7 purchase totals = $1,109.49       $1,163.1783   $1,163.18   $1,163.20   $1,163.30