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 $44.36   4.855%   $46.5137   $46.51   $46.50   $46.50  
  Purchase #2 $64.91   4.216%   $67.6466   $67.65   $67.65   $67.60  
  Purchase #3 $82.45   4.598%   $86.2411   $86.24   $86.25   $86.20  
  Purchase #4 $159.86   3.747%   $165.85   $165.85   $165.85   $165.90  
  Purchase #5 $176.31   9.833%   $193.6466   $193.65   $193.65   $193.60  
  Purchase #6 $162.99   8.357%   $176.6111   $176.61   $176.60   $176.60  
  Purchase #7 $167.61   7.776%   $180.6434   $180.64   $180.65   $180.60  
  7 purchase totals = $858.49       $917.1525   $917.15   $917.15   $917.00