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	$213.57	5.538%	$225.3975	$225.40	$225.40	$225.40
Purchase #2	$34.40	7.745%	$37.0643	$37.06	$37.05	$37.10
Purchase #3	$179.32	4.731%	$187.8036	$187.80	$187.80	$187.80
Purchase #4	$36.88	12.330%	$41.4273	$41.43	$41.45	$41.40
Purchase #5	$49.85	4.621%	$52.1536	$52.15	$52.15	$52.20
Purchase #6	$115.83	12.684%	$130.5219	$130.52	$130.50	$130.50
Purchase #7	$175.39	11.421%	$195.4213	$195.42	$195.40	$195.40
7 purchase totals =	$805.24		$869.7895	$869.78	$869.75	$869.80