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 $106.48   7.525%   $114.4926   $114.49   $114.50   $114.50  
  Purchase #2 $61.60   5.377%   $64.9122   $64.91   $64.90   $64.90  
  Purchase #3 $201.30   9.689%   $220.804   $220.80   $220.80   $220.80  
  Purchase #4 $114.91   5.455%   $121.1783   $121.18   $121.20   $121.20  
  Purchase #5 $208.45   11.441%   $232.2988   $232.30   $232.30   $232.30  
  Purchase #6 $163.49   5.295%   $172.1468   $172.15   $172.15   $172.10  
  Purchase #7 $83.50   8.698%   $90.7628   $90.76   $90.75   $90.80  
  7 purchase totals = $939.73       $1,016.5955   $1,016.59   $1,016.60   $1,016.60