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	$104.86	6.744%	$111.9318	$111.93	$111.95	$111.90
Purchase #2	$113.52	4.493%	$118.6205	$118.62	$118.60	$118.60
Purchase #3	$227.80	13.542%	$258.6487	$258.65	$258.65	$258.60
Purchase #4	$141.44	11.811%	$158.1455	$158.15	$158.15	$158.10
Purchase #5	$134.89	3.260%	$139.2874	$139.29	$139.30	$139.30
Purchase #6	$8.60	6.263%	$9.1386	$9.14	$9.15	$9.10
Purchase #7	$135.51	7.821%	$146.1082	$146.11	$146.10	$146.10
7 purchase totals =	$866.62		$941.8807	$941.89	$941.90	$941.70