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	$209.28	13.781%	$238.1209	$238.12	$238.10	$238.10
Purchase #2	$172.60	10.167%	$190.1482	$190.15	$190.15	$190.10
Purchase #3	$55.49	12.785%	$62.5844	$62.58	$62.60	$62.60
Purchase #4	$246.45	13.730%	$280.2876	$280.29	$280.30	$280.30
Purchase #5	$114.75	8.723%	$124.7596	$124.76	$124.75	$124.80
Purchase #6	$62.58	5.230%	$65.8529	$65.85	$65.85	$65.90
Purchase #7	$210.91	12.628%	$237.5437	$237.54	$237.55	$237.50
7 purchase totals =	$1,072.06		$1,199.2973	$1,199.29	$1,199.30	$1,199.30