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	$189.93	3.287%	$196.173	$196.17	$196.15	$196.20
Purchase #2	$38.65	9.746%	$42.4168	$42.42	$42.40	$42.40
Purchase #3	$9.35	6.152%	$9.9252	$9.93	$9.95	$9.90
Purchase #4	$110.72	10.242%	$122.0599	$122.06	$122.05	$122.10
Purchase #5	$69.93	10.554%	$77.3104	$77.31	$77.30	$77.30
Purchase #6	$33.62	8.528%	$36.4871	$36.49	$36.50	$36.50
Purchase #7	$72.64	7.568%	$78.1374	$78.14	$78.15	$78.10
7 purchase totals =	$524.84		$562.5098	$562.52	$562.50	$562.50