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	$114.96	11.511%	$128.193	$128.19	$128.20	$128.20
Purchase #2	$8.91	8.208%	$9.6413	$9.64	$9.65	$9.60
Purchase #3	$109.84	12.231%	$123.2745	$123.27	$123.25	$123.30
Purchase #4	$52.40	4.195%	$54.5982	$54.60	$54.60	$54.60
Purchase #5	$62.77	4.355%	$65.5036	$65.50	$65.50	$65.50
Purchase #6	$140.57	12.863%	$158.6515	$158.65	$158.65	$158.70
Purchase #7	$71.33	9.458%	$78.0764	$78.08	$78.10	$78.10
7 purchase totals =	$560.78		$617.9385	$617.93	$617.95	$618.00