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	$234.61	9.111%	$255.9853	$255.99	$256.00	$256.00
Purchase #2	$235.70	6.380%	$250.7377	$250.74	$250.75	$250.70
Purchase #3	$157.80	5.647%	$166.711	$166.71	$166.70	$166.70
Purchase #4	$109.82	6.202%	$116.631	$116.63	$116.65	$116.60
Purchase #5	$217.40	13.836%	$247.4795	$247.48	$247.50	$247.50
Purchase #6	$35.60	4.813%	$37.3134	$37.31	$37.30	$37.30
Purchase #7	$91.76	13.501%	$104.1485	$104.15	$104.15	$104.10
7 purchase totals =	$1,082.69		$1,179.0064	$1,179.01	$1,179.05	$1,178.90