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	$158.48	9.271%	$173.1727	$173.17	$173.15	$173.20
Purchase #2	$224.80	10.790%	$249.0559	$249.06	$249.05	$249.10
Purchase #3	$12.32	8.498%	$13.367	$13.37	$13.35	$13.40
Purchase #4	$83.42	7.257%	$89.4738	$89.47	$89.45	$89.50
Purchase #5	$130.80	13.580%	$148.5626	$148.56	$148.55	$148.60
Purchase #6	$114.77	8.165%	$124.141	$124.14	$124.15	$124.10
Purchase #7	$249.71	5.610%	$263.7187	$263.72	$263.70	$263.70
7 purchase totals =	$974.30		$1,061.4917	$1,061.49	$1,061.40	$1,061.60