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	$169.86	12.677%	$191.3932	$191.39	$191.40	$191.40
Purchase #2	$11.61	9.827%	$12.7509	$12.75	$12.75	$12.80
Purchase #3	$162.98	13.819%	$185.5022	$185.50	$185.50	$185.50
Purchase #4	$45.38	4.201%	$47.2864	$47.29	$47.30	$47.30
Purchase #5	$147.70	13.486%	$167.6188	$167.62	$167.60	$167.60
Purchase #6	$32.47	5.178%	$34.1513	$34.15	$34.15	$34.20
Purchase #7	$14.54	3.574%	$15.0597	$15.06	$15.05	$15.10
7 purchase totals =	$584.54		$653.7625	$653.76	$653.75	$653.90