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	$163.52	8.469%	$177.3685	$177.37	$177.35	$177.40
Purchase #2	$238.48	11.822%	$266.6731	$266.67	$266.65	$266.70
Purchase #3	$106.48	4.747%	$111.5346	$111.53	$111.55	$111.50
Purchase #4	$170.89	13.526%	$194.0046	$194.00	$194.00	$194.00
Purchase #5	$99.36	12.818%	$112.096	$112.10	$112.10	$112.10
Purchase #6	$88.35	13.482%	$100.2613	$100.26	$100.25	$100.30
Purchase #7	$238.32	12.238%	$267.4856	$267.49	$267.50	$267.50
7 purchase totals =	$1,105.40		$1,229.4237	$1,229.42	$1,229.40	$1,229.50