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	$64.86	11.772%	$72.4953	$72.50	$72.50	$72.50
Purchase #2	$168.72	11.856%	$188.7234	$188.72	$188.70	$188.70
Purchase #3	$27.28	7.432%	$29.3074	$29.31	$29.30	$29.30
Purchase #4	$107.27	5.706%	$113.3908	$113.39	$113.40	$113.40
Purchase #5	$151.83	4.316%	$158.383	$158.38	$158.40	$158.40
Purchase #6	$233.52	9.379%	$255.4218	$255.42	$255.40	$255.40
Purchase #7	$208.87	6.781%	$223.0335	$223.03	$223.05	$223.00
7 purchase totals =	$962.35		$1,040.7552	$1,040.75	$1,040.75	$1,040.70