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 $157.58   5.112%   $165.6355   $165.64   $165.65   $165.60  
  Purchase #2 $114.61   10.126%   $126.2154   $126.22   $126.20   $126.20  
  Purchase #3 $67.78   7.634%   $72.9543   $72.95   $72.95   $73.00  
  Purchase #4 $188.26   7.130%   $201.6829   $201.68   $201.70   $201.70  
  Purchase #5 $205.67   12.573%   $231.5289   $231.53   $231.55   $231.50  
  Purchase #6 $116.95   13.204%   $132.3921   $132.39   $132.40   $132.40  
  Purchase #7 $165.65   8.611%   $179.9141   $179.91   $179.90   $179.90  
  7 purchase totals = $1,016.50       $1,110.3232   $1,110.32   $1,110.35   $1,110.30