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	$196.41	12.644%	$221.2441	$221.24	$221.25	$221.20
Purchase #2	$146.36	13.479%	$166.0879	$166.09	$166.10	$166.10
Purchase #3	$164.61	9.414%	$180.1064	$180.11	$180.10	$180.10
Purchase #4	$119.94	9.682%	$131.5526	$131.55	$131.55	$131.60
Purchase #5	$146.60	4.499%	$153.1955	$153.20	$153.20	$153.20
Purchase #6	$132.32	7.771%	$142.6026	$142.60	$142.60	$142.60
Purchase #7	$171.77	3.718%	$178.1564	$178.16	$178.15	$178.20
7 purchase totals =	$1,078.01		$1,172.9455	$1,172.95	$1,172.95	$1,173.00