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 $201.79   10.800%   $223.5833   $223.58   $223.60   $223.60  
  Purchase #2 $113.95   9.446%   $124.7137   $124.71   $124.70   $124.70  
  Purchase #3 $56.49   8.437%   $61.2561   $61.26   $61.25   $61.30  
  Purchase #4 $202.58   13.685%   $230.3031   $230.30   $230.30   $230.30  
  Purchase #5 $40.82   6.732%   $43.568   $43.57   $43.55   $43.60  
  Purchase #6 $147.62   10.693%   $163.405   $163.41   $163.40   $163.40  
  Purchase #7 $226.69   9.738%   $248.7651   $248.77   $248.75   $248.80  
  7 purchase totals = $989.94       $1,095.5943   $1,095.60   $1,095.55   $1,095.70