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	$215.61	3.466%	$223.083	$223.08	$223.10	$223.10
Purchase #2	$168.78	7.729%	$181.825	$181.83	$181.85	$181.80
Purchase #3	$37.40	4.553%	$39.1028	$39.10	$39.10	$39.10
Purchase #4	$159.58	8.670%	$173.4156	$173.42	$173.40	$173.40
Purchase #5	$106.78	9.236%	$116.6422	$116.64	$116.65	$116.60
Purchase #6	$5.47	11.541%	$6.1013	$6.10	$6.10	$6.10
Purchase #7	$53.87	3.719%	$55.8734	$55.87	$55.85	$55.90
7 purchase totals =	$747.49		$796.0433	$796.04	$796.05	$796.00