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	$223.35	4.634%	$233.7	$233.70	$233.70	$233.70
Purchase #2	$105.84	8.107%	$114.4204	$114.42	$114.40	$114.40
Purchase #3	$203.60	9.434%	$222.8076	$222.81	$222.80	$222.80
Purchase #4	$98.49	12.780%	$111.077	$111.08	$111.10	$111.10
Purchase #5	$9.60	8.467%	$10.4128	$10.41	$10.40	$10.40
Purchase #6	$217.38	10.569%	$240.3549	$240.35	$240.35	$240.40
Purchase #7	$76.50	3.645%	$79.2884	$79.29	$79.30	$79.30
7 purchase totals =	$934.76		$1,012.0611	$1,012.06	$1,012.05	$1,012.10