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 $116.39   8.290%   $126.0387   $126.04   $126.05   $126.00  
  Purchase #2 $123.92   10.422%   $136.8349   $136.83   $136.85   $136.80  
  Purchase #3 $213.63   7.342%   $229.3147   $229.31   $229.30   $229.30  
  Purchase #4 $13.85   11.750%   $15.4774   $15.48   $15.50   $15.50  
  Purchase #5 $214.46   7.462%   $230.463   $230.46   $230.45   $230.50  
  Purchase #6 $228.30   3.483%   $236.2517   $236.25   $236.25   $236.30  
  Purchase #7 $49.51   5.330%   $52.1489   $52.15   $52.15   $52.10  
  7 purchase totals = $960.06       $1,026.5293   $1,026.52   $1,026.55   $1,026.50