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	$52.67	3.386%	$54.4534	$54.45	$54.45	$54.50
Purchase #2	$29.69	8.717%	$32.2781	$32.28	$32.30	$32.30
Purchase #3	$54.75	4.200%	$57.0495	$57.05	$57.05	$57.00
Purchase #4	$174.73	10.777%	$193.5607	$193.56	$193.55	$193.60
Purchase #5	$180.37	8.719%	$196.0965	$196.10	$196.10	$196.10
Purchase #6	$94.31	6.788%	$100.7118	$100.71	$100.70	$100.70
Purchase #7	$78.68	7.845%	$84.8524	$84.85	$84.85	$84.90
7 purchase totals =	$665.20		$719.0024	$719.00	$719.00	$719.10