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	$38.72	12.538%	$43.5747	$43.57	$43.55	$43.60
Purchase #2	$208.97	8.716%	$227.1838	$227.18	$227.20	$227.20
Purchase #3	$154.98	7.505%	$166.6112	$166.61	$166.60	$166.60
Purchase #4	$7.88	6.342%	$8.3797	$8.38	$8.40	$8.40
Purchase #5	$177.93	12.862%	$200.8154	$200.82	$200.80	$200.80
Purchase #6	$193.56	7.556%	$208.1854	$208.19	$208.20	$208.20
Purchase #7	$196.93	13.440%	$223.3974	$223.40	$223.40	$223.40
7 purchase totals =	$978.97		$1,078.1476	$1,078.15	$1,078.15	$1,078.20