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	$70.91	11.346%	$78.9554	$78.96	$78.95	$79.00
Purchase #2	$177.30	5.726%	$187.4522	$187.45	$187.45	$187.50
Purchase #3	$124.65	5.597%	$131.6267	$131.63	$131.65	$131.60
Purchase #4	$105.62	8.209%	$114.2903	$114.29	$114.30	$114.30
Purchase #5	$202.71	11.153%	$225.3182	$225.32	$225.30	$225.30
Purchase #6	$45.57	12.251%	$51.1528	$51.15	$51.15	$51.20
Purchase #7	$155.84	5.612%	$164.5857	$164.59	$164.60	$164.60
7 purchase totals =	$882.60		$953.3813	$953.39	$953.40	$953.50