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	$44.68	3.449%	$46.221	$46.22	$46.20	$46.20
Purchase #2	$197.31	6.336%	$209.8116	$209.81	$209.80	$209.80
Purchase #3	$103.58	11.601%	$115.5963	$115.60	$115.60	$115.60
Purchase #4	$41.45	10.849%	$45.9469	$45.95	$45.95	$45.90
Purchase #5	$187.38	11.693%	$209.2903	$209.29	$209.30	$209.30
Purchase #6	$84.92	5.445%	$89.5439	$89.54	$89.55	$89.50
Purchase #7	$66.37	6.426%	$70.6349	$70.63	$70.65	$70.60
7 purchase totals =	$725.69		$787.0449	$787.04	$787.05	$786.90