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 $82.54   12.260%   $92.6594   $92.66   $92.65   $92.70  
  Purchase #2 $158.95   13.488%   $180.3892   $180.39   $180.40   $180.40  
  Purchase #3 $216.93   13.458%   $246.1244   $246.12   $246.10   $246.10  
  Purchase #4 $102.97   11.337%   $114.6437   $114.64   $114.65   $114.60  
  Purchase #5 $164.41   5.591%   $173.6022   $173.60   $173.60   $173.60  
  Purchase #6 $190.57   12.423%   $214.2445   $214.24   $214.25   $214.20  
  Purchase #7 $197.48   8.584%   $214.4317   $214.43   $214.45   $214.40  
  7 purchase totals = $1,113.85       $1,236.0951   $1,236.08   $1,236.10   $1,236.00