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 $94.99   3.382%   $98.2026   $98.20   $98.20   $98.20  
  Purchase #2 $6.87   10.753%   $7.6087   $7.61   $7.60   $7.60  
  Purchase #3 $100.97   12.487%   $113.5781   $113.58   $113.60   $113.60  
  Purchase #4 $230.40   12.484%   $259.1631   $259.16   $259.15   $259.20  
  Purchase #5 $220.32   11.230%   $245.0619   $245.06   $245.05   $245.10  
  Purchase #6 $105.49   10.455%   $116.519   $116.52   $116.50   $116.50  
  Purchase #7 $182.42   5.864%   $193.1171   $193.12   $193.10   $193.10  
  7 purchase totals = $941.46       $1,033.2505   $1,033.25   $1,033.20   $1,033.30