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	$219.78	11.149%	$244.2833	$244.28	$244.30	$244.30
Purchase #2	$198.69	13.603%	$225.7178	$225.72	$225.70	$225.70
Purchase #3	$190.26	11.113%	$211.4036	$211.40	$211.40	$211.40
Purchase #4	$205.85	8.541%	$223.4316	$223.43	$223.45	$223.40
Purchase #5	$59.46	12.759%	$67.0465	$67.05	$67.05	$67.00
Purchase #6	$208.95	7.859%	$225.3714	$225.37	$225.35	$225.40
Purchase #7	$102.41	6.585%	$109.1537	$109.15	$109.15	$109.20
7 purchase totals =	$1,185.40		$1,306.4079	$1,306.40	$1,306.40	$1,306.40