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	$159.78	11.322%	$177.8703	$177.87	$177.85	$177.90
Purchase #2	$168.83	13.560%	$191.7233	$191.72	$191.70	$191.70
Purchase #3	$52.46	7.203%	$56.2387	$56.24	$56.25	$56.20
Purchase #4	$191.95	7.269%	$205.9028	$205.90	$205.90	$205.90
Purchase #5	$55.46	7.171%	$59.437	$59.44	$59.45	$59.40
Purchase #6	$214.84	3.360%	$222.0586	$222.06	$222.05	$222.10
Purchase #7	$22.61	3.160%	$23.3245	$23.32	$23.30	$23.30
7 purchase totals =	$865.93		$936.5552	$936.55	$936.50	$936.50