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	$155.75	3.693%	$161.5018	$161.50	$161.50	$161.50
Purchase #2	$117.52	8.298%	$127.2718	$127.27	$127.25	$127.30
Purchase #3	$195.69	4.247%	$204.001	$204.00	$204.00	$204.00
Purchase #4	$139.50	6.355%	$148.3652	$148.37	$148.35	$148.40
Purchase #5	$76.36	12.819%	$86.1486	$86.15	$86.15	$86.10
Purchase #6	$196.89	10.545%	$217.6521	$217.65	$217.65	$217.70
Purchase #7	$115.33	10.552%	$127.4996	$127.50	$127.50	$127.50
7 purchase totals =	$997.04		$1,072.4401	$1,072.44	$1,072.40	$1,072.50