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	$178.79	13.365%	$202.6853	$202.69	$202.70	$202.70
Purchase #2	$114.85	8.714%	$124.858	$124.86	$124.85	$124.90
Purchase #3	$237.70	10.333%	$262.2615	$262.26	$262.25	$262.30
Purchase #4	$198.57	12.608%	$223.6057	$223.61	$223.60	$223.60
Purchase #5	$139.56	8.549%	$151.491	$151.49	$151.50	$151.50
Purchase #6	$205.75	13.593%	$233.7176	$233.72	$233.70	$233.70
Purchase #7	$52.84	12.834%	$59.6215	$59.62	$59.60	$59.60
7 purchase totals =	$1,128.06		$1,258.2406	$1,258.25	$1,258.20	$1,258.30