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	$91.82	9.407%	$100.4575	$100.46	$100.45	$100.50
Purchase #2	$31.64	4.416%	$33.0372	$33.04	$33.05	$33.00
Purchase #3	$67.60	6.161%	$71.7648	$71.76	$71.75	$71.80
Purchase #4	$83.46	8.196%	$90.3004	$90.30	$90.30	$90.30
Purchase #5	$212.31	6.784%	$226.7131	$226.71	$226.70	$226.70
Purchase #6	$158.38	5.207%	$166.6268	$166.63	$166.65	$166.60
Purchase #7	$64.39	4.209%	$67.1002	$67.10	$67.10	$67.10
7 purchase totals =	$709.60		$756.0000	$756.00	$756.00	$756.00