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 $67.92   4.738%   $71.138   $71.14   $71.15   $71.10  
  Purchase #2 $107.36   8.542%   $116.5307   $116.53   $116.55   $116.50  
  Purchase #3 $105.95   9.148%   $115.6423   $115.64   $115.65   $115.60  
  Purchase #4 $86.92   5.444%   $91.6519   $91.65   $91.65   $91.70  
  Purchase #5 $108.26   6.651%   $115.4604   $115.46   $115.45   $115.50  
  Purchase #6 $136.96   5.584%   $144.6078   $144.61   $144.60   $144.60  
  Purchase #7 $103.39   3.705%   $107.2206   $107.22   $107.20   $107.20  
  7 purchase totals = $716.76       $762.2517   $762.25   $762.25   $762.20