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	$46.61	10.805%	$51.6462	$51.65	$51.65	$51.60
Purchase #2	$51.72	6.144%	$54.8977	$54.90	$54.90	$54.90
Purchase #3	$51.83	3.675%	$53.7348	$53.73	$53.75	$53.70
Purchase #4	$44.89	13.712%	$51.0453	$51.05	$51.05	$51.00
Purchase #5	$145.78	12.694%	$164.2853	$164.29	$164.30	$164.30
Purchase #6	$22.64	7.638%	$24.3692	$24.37	$24.35	$24.40
Purchase #7	$92.77	13.291%	$105.1001	$105.10	$105.10	$105.10
7 purchase totals =	$456.24		$505.0786	$505.09	$505.10	$505.00