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	$182.70	6.617%	$194.7893	$194.79	$194.80	$194.80
Purchase #2	$173.81	12.852%	$196.1481	$196.15	$196.15	$196.10
Purchase #3	$107.35	3.828%	$111.4594	$111.46	$111.45	$111.50
Purchase #4	$25.56	10.796%	$28.3195	$28.32	$28.30	$28.30
Purchase #5	$125.45	11.452%	$139.8165	$139.82	$139.80	$139.80
Purchase #6	$171.47	6.705%	$182.9671	$182.97	$182.95	$183.00
Purchase #7	$126.63	5.359%	$133.4161	$133.42	$133.40	$133.40
7 purchase totals =	$912.97		$986.9160	$986.93	$986.85	$986.90