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 $70.67   5.607%   $74.6325   $74.63   $74.65   $74.60  
  Purchase #2 $191.82   9.836%   $210.6874   $210.69   $210.70   $210.70  
  Purchase #3 $185.31   3.749%   $192.2573   $192.26   $192.25   $192.30  
  Purchase #4 $116.61   4.383%   $121.721   $121.72   $121.70   $121.70  
  Purchase #5 $173.83   3.243%   $179.4673   $179.47   $179.45   $179.50  
  Purchase #6 $235.40   4.512%   $246.0212   $246.02   $246.00   $246.00  
  Purchase #7 $87.81   4.169%   $91.4708   $91.47   $91.45   $91.50  
  7 purchase totals = $1,061.45       $1,116.2575   $1,116.26   $1,116.20   $1,116.30