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	$40.29	8.113%	$43.5587	$43.56	$43.55	$43.60
Purchase #2	$103.92	9.114%	$113.3913	$113.39	$113.40	$113.40
Purchase #3	$50.83	7.762%	$54.7754	$54.78	$54.80	$54.80
Purchase #4	$221.38	4.256%	$230.8019	$230.80	$230.80	$230.80
Purchase #5	$85.55	10.127%	$94.2136	$94.21	$94.20	$94.20
Purchase #6	$192.62	6.863%	$205.8395	$205.84	$205.85	$205.80
Purchase #7	$240.75	10.440%	$265.8843	$265.88	$265.90	$265.90
7 purchase totals =	$935.34		$1,008.4647	$1,008.46	$1,008.50	$1,008.50