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	$69.40	13.792%	$78.9716	$78.97	$78.95	$79.00
Purchase #2	$184.98	12.789%	$208.6371	$208.64	$208.65	$208.60
Purchase #3	$248.30	6.267%	$263.861	$263.86	$263.85	$263.90
Purchase #4	$84.62	8.557%	$91.8609	$91.86	$91.85	$91.90
Purchase #5	$91.72	9.232%	$100.1876	$100.19	$100.20	$100.20
Purchase #6	$144.39	11.307%	$160.7162	$160.72	$160.70	$160.70
Purchase #7	$95.68	6.156%	$101.5701	$101.57	$101.55	$101.60
7 purchase totals =	$919.09		$1,005.8045	$1,005.81	$1,005.75	$1,005.90