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 $68.45   5.642%   $72.3119   $72.31   $72.30   $72.30  
  Purchase #2 $144.31   3.669%   $149.6047   $149.60   $149.60   $149.60  
  Purchase #3 $104.92   9.279%   $114.6555   $114.66   $114.65   $114.70  
  Purchase #4 $220.70   5.724%   $233.3329   $233.33   $233.35   $233.30  
  Purchase #5 $129.77   3.455%   $134.2536   $134.25   $134.25   $134.30  
  Purchase #6 $113.29   3.243%   $116.964   $116.96   $116.95   $117.00  
  Purchase #7 $72.62   5.806%   $76.8363   $76.84   $76.85   $76.80  
  7 purchase totals = $854.06       $897.9589   $897.95   $897.95   $898.00