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 $86.33   8.406%   $93.5869   $93.59   $93.60   $93.60  
  Purchase #2 $197.58   5.265%   $207.9826   $207.98   $208.00   $208.00  
  Purchase #3 $106.50   5.426%   $112.2787   $112.28   $112.30   $112.30  
  Purchase #4 $40.96   12.637%   $46.1361   $46.14   $46.15   $46.10  
  Purchase #5 $225.93   12.679%   $254.5757   $254.58   $254.60   $254.60  
  Purchase #6 $223.76   3.453%   $231.4864   $231.49   $231.50   $231.50  
  Purchase #7 $235.65   11.346%   $262.3868   $262.39   $262.40   $262.40  
  7 purchase totals = $1,116.71       $1,208.4332   $1,208.45   $1,208.55   $1,208.50