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	$47.56	4.182%	$49.549	$49.55	$49.55	$49.50
Purchase #2	$59.91	9.419%	$65.5529	$65.55	$65.55	$65.60
Purchase #3	$85.35	3.705%	$88.5122	$88.51	$88.50	$88.50
Purchase #4	$217.67	9.380%	$238.0874	$238.09	$238.10	$238.10
Purchase #5	$147.51	7.140%	$158.0422	$158.04	$158.05	$158.00
Purchase #6	$67.81	6.181%	$72.0013	$72.00	$72.00	$72.00
Purchase #7	$13.70	11.720%	$15.3056	$15.31	$15.30	$15.30
7 purchase totals =	$639.51		$687.0506	$687.05	$687.05	$687.00