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	$171.69	7.408%	$184.4088	$184.41	$184.40	$184.40
Purchase #2	$85.91	3.701%	$89.0895	$89.09	$89.10	$89.10
Purchase #3	$50.78	7.255%	$54.4641	$54.46	$54.45	$54.50
Purchase #4	$121.27	4.473%	$126.6944	$126.69	$126.70	$126.70
Purchase #5	$160.44	10.798%	$177.7643	$177.76	$177.75	$177.80
Purchase #6	$55.96	6.653%	$59.683	$59.68	$59.70	$59.70
Purchase #7	$49.51	5.347%	$52.1573	$52.16	$52.15	$52.20
7 purchase totals =	$695.56		$744.2614	$744.25	$744.25	$744.40