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	$222.53	4.777%	$233.1603	$233.16	$233.15	$233.20
Purchase #2	$170.52	9.140%	$186.1055	$186.11	$186.10	$186.10
Purchase #3	$246.84	10.504%	$272.7681	$272.77	$272.75	$272.80
Purchase #4	$171.75	7.771%	$185.0967	$185.10	$185.10	$185.10
Purchase #5	$86.65	3.354%	$89.5562	$89.56	$89.55	$89.60
Purchase #6	$10.82	4.448%	$11.3013	$11.30	$11.30	$11.30
Purchase #7	$130.65	11.431%	$145.5846	$145.58	$145.60	$145.60
7 purchase totals =	$1,039.76		$1,123.5727	$1,123.58	$1,123.55	$1,123.70