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	$172.88	7.228%	$185.3758	$185.38	$185.40	$185.40
Purchase #2	$246.57	4.755%	$258.2944	$258.29	$258.30	$258.30
Purchase #3	$37.55	9.536%	$41.1308	$41.13	$41.15	$41.10
Purchase #4	$115.67	13.712%	$131.5307	$131.53	$131.55	$131.50
Purchase #5	$48.27	3.311%	$49.8682	$49.87	$49.85	$49.90
Purchase #6	$54.56	6.323%	$58.0098	$58.01	$58.00	$58.00
Purchase #7	$217.79	4.491%	$227.5709	$227.57	$227.55	$227.60
7 purchase totals =	$893.29		$951.7806	$951.78	$951.80	$951.80