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	$215.52	8.472%	$233.7789	$233.78	$233.80	$233.80
Purchase #2	$102.70	6.802%	$109.6857	$109.69	$109.70	$109.70
Purchase #3	$212.87	13.383%	$241.3584	$241.36	$241.35	$241.40
Purchase #4	$237.84	6.548%	$253.4138	$253.41	$253.40	$253.40
Purchase #5	$68.75	12.860%	$77.5913	$77.59	$77.60	$77.60
Purchase #6	$172.25	7.717%	$185.5425	$185.54	$185.55	$185.50
Purchase #7	$54.78	3.307%	$56.5916	$56.59	$56.60	$56.60
7 purchase totals =	$1,064.71		$1,157.9622	$1,157.96	$1,158.00	$1,158.00