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 $44.76   9.371%   $48.9545   $48.95   $48.95   $49.00  
  Purchase #2 $83.99   3.553%   $86.9742   $86.97   $86.95   $87.00  
  Purchase #3 $93.36   5.481%   $98.4771   $98.48   $98.50   $98.50  
  Purchase #4 $153.68   8.782%   $167.1762   $167.18   $167.20   $167.20  
  Purchase #5 $237.26   4.712%   $248.4397   $248.44   $248.45   $248.40  
  Purchase #6 $8.37   12.541%   $9.4197   $9.42   $9.40   $9.40  
  Purchase #7 $123.31   11.167%   $137.08   $137.08   $137.10   $137.10  
  7 purchase totals = $744.73       $796.5214   $796.52   $796.55   $796.60