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	$238.98	3.121%	$246.4386	$246.44	$246.45	$246.40
Purchase #2	$196.51	6.241%	$208.7742	$208.77	$208.75	$208.80
Purchase #3	$19.37	9.136%	$21.1396	$21.14	$21.15	$21.10
Purchase #4	$177.59	10.538%	$196.3044	$196.30	$196.30	$196.30
Purchase #5	$141.58	13.662%	$160.9227	$160.92	$160.90	$160.90
Purchase #6	$37.35	11.466%	$41.6326	$41.63	$41.65	$41.60
Purchase #7	$219.74	13.137%	$248.6072	$248.61	$248.60	$248.60
7 purchase totals =	$1,031.12		$1,123.8193	$1,123.81	$1,123.80	$1,123.70