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	$244.46	8.571%	$265.4127	$265.41	$265.40	$265.40
Purchase #2	$180.78	12.636%	$203.6234	$203.62	$203.60	$203.60
Purchase #3	$174.78	7.291%	$187.5232	$187.52	$187.50	$187.50
Purchase #4	$244.66	13.332%	$277.2781	$277.28	$277.30	$277.30
Purchase #5	$128.59	7.244%	$137.9051	$137.91	$137.90	$137.90
Purchase #6	$57.81	12.252%	$64.8929	$64.89	$64.90	$64.90
Purchase #7	$233.81	5.502%	$246.6742	$246.67	$246.65	$246.70
7 purchase totals =	$1,264.89		$1,383.3096	$1,383.30	$1,383.25	$1,383.30