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	$157.72	9.428%	$172.5898	$172.59	$172.60	$172.60
Purchase #2	$248.58	8.360%	$269.3613	$269.36	$269.35	$269.40
Purchase #3	$246.83	3.675%	$255.901	$255.90	$255.90	$255.90
Purchase #4	$31.55	9.209%	$34.4554	$34.46	$34.45	$34.50
Purchase #5	$217.31	9.653%	$238.2869	$238.29	$238.30	$238.30
Purchase #6	$178.41	8.579%	$193.7158	$193.72	$193.70	$193.70
Purchase #7	$43.58	8.493%	$47.2812	$47.28	$47.30	$47.30
7 purchase totals =	$1,123.98		$1,211.5914	$1,211.60	$1,211.60	$1,211.70