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	$245.27	9.475%	$268.5093	$268.51	$268.50	$268.50
Purchase #2	$215.52	5.271%	$226.8801	$226.88	$226.90	$226.90
Purchase #3	$92.58	12.264%	$103.934	$103.93	$103.95	$103.90
Purchase #4	$204.61	12.472%	$230.129	$230.13	$230.15	$230.10
Purchase #5	$246.52	13.505%	$279.8125	$279.81	$279.80	$279.80
Purchase #6	$29.53	13.184%	$33.4232	$33.42	$33.40	$33.40
Purchase #7	$105.32	5.745%	$111.3706	$111.37	$111.35	$111.40
7 purchase totals =	$1,139.35		$1,254.0587	$1,254.05	$1,254.05	$1,254.00