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	$189.78	13.607%	$215.6034	$215.60	$215.60	$215.60
Purchase #2	$191.69	9.174%	$209.2756	$209.28	$209.30	$209.30
Purchase #3	$239.73	6.563%	$255.4635	$255.46	$255.45	$255.50
Purchase #4	$172.69	3.162%	$178.1505	$178.15	$178.15	$178.20
Purchase #5	$117.56	13.453%	$133.3753	$133.38	$133.40	$133.40
Purchase #6	$189.46	5.329%	$199.5563	$199.56	$199.55	$199.60
Purchase #7	$197.43	3.488%	$204.3164	$204.32	$204.30	$204.30
7 purchase totals =	$1,298.34		$1,395.7410	$1,395.75	$1,395.75	$1,395.90