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	$105.32	4.144%	$109.6845	$109.68	$109.70	$109.70
Purchase #2	$40.95	8.462%	$44.4152	$44.42	$44.40	$44.40
Purchase #3	$185.89	10.507%	$205.4215	$205.42	$205.40	$205.40
Purchase #4	$55.63	10.150%	$61.2764	$61.28	$61.30	$61.30
Purchase #5	$159.42	8.539%	$173.0329	$173.03	$173.05	$173.00
Purchase #6	$29.79	5.495%	$31.427	$31.43	$31.45	$31.40
Purchase #7	$48.76	4.605%	$51.0054	$51.01	$51.00	$51.00
7 purchase totals =	$625.76		$676.2629	$676.27	$676.30	$676.20