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	$226.98	10.403%	$250.5927	$250.59	$250.60	$250.60
Purchase #2	$185.72	10.760%	$205.7035	$205.70	$205.70	$205.70
Purchase #3	$110.67	6.604%	$117.9786	$117.98	$118.00	$118.00
Purchase #4	$172.51	5.230%	$181.5323	$181.53	$181.55	$181.50
Purchase #5	$107.41	7.146%	$115.0855	$115.09	$115.10	$115.10
Purchase #6	$203.84	5.617%	$215.2897	$215.29	$215.30	$215.30
Purchase #7	$103.69	6.490%	$110.4195	$110.42	$110.40	$110.40
7 purchase totals =	$1,110.82		$1,196.6018	$1,196.60	$1,196.65	$1,196.60