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 $62.52   11.567%   $69.7517   $69.75   $69.75   $69.80  
  Purchase #2 $220.59   7.367%   $236.8409   $236.84   $236.85   $236.80  
  Purchase #3 $81.66   11.339%   $90.9194   $90.92   $90.90   $90.90  
  Purchase #4 $171.68   10.723%   $190.0892   $190.09   $190.10   $190.10  
  Purchase #5 $139.85   12.671%   $157.5704   $157.57   $157.55   $157.60  
  Purchase #6 $139.31   6.210%   $147.9612   $147.96   $147.95   $148.00  
  Purchase #7 $126.96   7.426%   $136.388   $136.39   $136.40   $136.40  
  7 purchase totals = $942.57       $1,029.5208   $1,029.52   $1,029.50   $1,029.60