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	$158.42	4.636%	$165.7644	$165.76	$165.75	$165.80
Purchase #2	$225.42	5.309%	$237.3875	$237.39	$237.40	$237.40
Purchase #3	$208.25	7.861%	$224.6205	$224.62	$224.60	$224.60
Purchase #4	$232.80	4.202%	$242.5823	$242.58	$242.60	$242.60
Purchase #5	$156.84	10.229%	$172.8832	$172.88	$172.90	$172.90
Purchase #6	$187.55	5.613%	$198.0772	$198.08	$198.10	$198.10
Purchase #7	$59.86	12.628%	$67.4191	$67.42	$67.40	$67.40
7 purchase totals =	$1,229.14		$1,308.7342	$1,308.73	$1,308.75	$1,308.80