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	$164.49	13.634%	$186.9166	$186.92	$186.90	$186.90
Purchase #2	$136.49	4.586%	$142.7494	$142.75	$142.75	$142.70
Purchase #3	$103.47	10.509%	$114.3437	$114.34	$114.35	$114.30
Purchase #4	$169.52	3.475%	$175.4108	$175.41	$175.40	$175.40
Purchase #5	$41.64	9.164%	$45.4559	$45.46	$45.45	$45.50
Purchase #6	$155.42	12.566%	$174.9501	$174.95	$174.95	$175.00
Purchase #7	$250.55	8.469%	$271.7691	$271.77	$271.75	$271.80
7 purchase totals =	$1,021.58		$1,111.5956	$1,111.60	$1,111.55	$1,111.60