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	$151.37	13.860%	$172.3499	$172.35	$172.35	$172.30
Purchase #2	$70.46	3.144%	$72.6753	$72.68	$72.70	$72.70
Purchase #3	$147.90	12.334%	$166.142	$166.14	$166.15	$166.10
Purchase #4	$237.50	11.145%	$263.9694	$263.97	$263.95	$264.00
Purchase #5	$100.31	3.776%	$104.0977	$104.10	$104.10	$104.10
Purchase #6	$12.29	8.326%	$13.3133	$13.31	$13.30	$13.30
Purchase #7	$56.59	11.583%	$63.1448	$63.14	$63.15	$63.10
7 purchase totals =	$776.42		$855.6924	$855.69	$855.70	$855.60