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	$112.59	11.366%	$125.387	$125.39	$125.40	$125.40
Purchase #2	$100.69	10.348%	$111.1094	$111.11	$111.10	$111.10
Purchase #3	$223.89	11.726%	$250.1433	$250.14	$250.15	$250.10
Purchase #4	$130.42	12.520%	$146.7486	$146.75	$146.75	$146.70
Purchase #5	$215.68	5.779%	$228.1441	$228.14	$228.15	$228.10
Purchase #6	$50.97	8.492%	$55.2984	$55.30	$55.30	$55.30
Purchase #7	$10.54	4.456%	$11.0097	$11.01	$11.00	$11.00
7 purchase totals =	$844.78		$927.8405	$927.84	$927.85	$927.70