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	$40.76	8.585%	$44.2592	$44.26	$44.25	$44.30
Purchase #2	$190.86	7.665%	$205.4894	$205.49	$205.50	$205.50
Purchase #3	$159.87	3.698%	$165.782	$165.78	$165.80	$165.80
Purchase #4	$107.25	9.393%	$117.324	$117.32	$117.30	$117.30
Purchase #5	$196.95	13.699%	$223.9302	$223.93	$223.95	$223.90
Purchase #6	$54.63	12.764%	$61.603	$61.60	$61.60	$61.60
Purchase #7	$29.97	4.516%	$31.3234	$31.32	$31.30	$31.30
7 purchase totals =	$780.29		$849.7112	$849.70	$849.70	$849.70