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	$188.84	11.814%	$211.1496	$211.15	$211.15	$211.10
Purchase #2	$200.47	12.617%	$225.7633	$225.76	$225.75	$225.80
Purchase #3	$119.49	3.333%	$123.4726	$123.47	$123.45	$123.50
Purchase #4	$223.58	4.473%	$233.5807	$233.58	$233.60	$233.60
Purchase #5	$153.31	8.827%	$166.8427	$166.84	$166.85	$166.80
Purchase #6	$139.43	11.510%	$155.4784	$155.48	$155.50	$155.50
Purchase #7	$63.50	8.153%	$68.6772	$68.68	$68.70	$68.70
7 purchase totals =	$1,088.62		$1,184.9645	$1,184.96	$1,185.00	$1,185.00