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 $62.93   9.597%   $68.9694   $68.97   $68.95   $69.00  
  Purchase #2 $218.37   8.344%   $236.5908   $236.59   $236.60   $236.60  
  Purchase #3 $137.42   10.481%   $151.823   $151.82   $151.80   $151.80  
  Purchase #4 $212.97   6.717%   $227.2752   $227.28   $227.30   $227.30  
  Purchase #5 $242.91   9.366%   $265.661   $265.66   $265.65   $265.70  
  Purchase #6 $209.42   13.503%   $237.698   $237.70   $237.70   $237.70  
  Purchase #7 $209.65   6.280%   $222.816   $222.82   $222.80   $222.80  
  7 purchase totals = $1,293.67       $1,410.8334   $1,410.84   $1,410.80   $1,410.90