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	$154.58	8.646%	$167.945	$167.95	$167.95	$167.90
Purchase #2	$248.61	7.770%	$267.927	$267.93	$267.95	$267.90
Purchase #3	$208.59	11.845%	$233.2975	$233.30	$233.30	$233.30
Purchase #4	$144.83	6.356%	$154.0354	$154.04	$154.05	$154.00
Purchase #5	$56.98	9.244%	$62.2472	$62.25	$62.25	$62.20
Purchase #6	$190.29	3.395%	$196.7503	$196.75	$196.75	$196.80
Purchase #7	$154.71	8.295%	$167.5432	$167.54	$167.55	$167.50
7 purchase totals =	$1,158.59		$1,249.7456	$1,249.76	$1,249.80	$1,249.60