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 $147.33   3.271%   $152.1492   $152.15   $152.15   $152.10  
  Purchase #2 $53.65   10.855%   $59.4737   $59.47   $59.45   $59.50  
  Purchase #3 $143.54   12.267%   $161.1481   $161.15   $161.15   $161.10  
  Purchase #4 $223.28   11.197%   $248.2807   $248.28   $248.30   $248.30  
  Purchase #5 $124.89   6.171%   $132.597   $132.60   $132.60   $132.60  
  Purchase #6 $194.32   3.652%   $201.4166   $201.42   $201.40   $201.40  
  Purchase #7 $202.60   12.386%   $227.694   $227.69   $227.70   $227.70  
  7 purchase totals = $1,089.61       $1,182.7593   $1,182.76   $1,182.75   $1,182.70