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	$190.32	5.444%	$200.681	$200.68	$200.70	$200.70
Purchase #2	$129.49	9.736%	$142.0971	$142.10	$142.10	$142.10
Purchase #3	$178.64	10.178%	$196.822	$196.82	$196.80	$196.80
Purchase #4	$170.61	13.858%	$194.2531	$194.25	$194.25	$194.30
Purchase #5	$125.38	3.268%	$129.4774	$129.48	$129.50	$129.50
Purchase #6	$40.90	6.149%	$43.4149	$43.41	$43.40	$43.40
Purchase #7	$171.64	5.429%	$180.9583	$180.96	$180.95	$181.00
7 purchase totals =	$1,006.98		$1,087.7038	$1,087.70	$1,087.70	$1,087.80