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	$74.95	10.601%	$82.8954	$82.90	$82.90	$82.90
Purchase #2	$199.32	5.359%	$210.0016	$210.00	$210.00	$210.00
Purchase #3	$58.92	3.719%	$61.1112	$61.11	$61.10	$61.10
Purchase #4	$246.38	4.859%	$258.3516	$258.35	$258.35	$258.40
Purchase #5	$248.58	7.758%	$267.8648	$267.86	$267.85	$267.90
Purchase #6	$24.77	10.573%	$27.3889	$27.39	$27.40	$27.40
Purchase #7	$238.87	6.603%	$254.6426	$254.64	$254.65	$254.60
7 purchase totals =	$1,091.79		$1,162.2561	$1,162.25	$1,162.25	$1,162.30