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	$183.56	5.857%	$194.3111	$194.31	$194.30	$194.30
Purchase #2	$12.33	6.156%	$13.089	$13.09	$13.10	$13.10
Purchase #3	$71.83	11.202%	$79.8764	$79.88	$79.90	$79.90
Purchase #4	$104.61	4.455%	$109.2704	$109.27	$109.25	$109.30
Purchase #5	$19.94	9.632%	$21.8606	$21.86	$21.85	$21.90
Purchase #6	$85.71	8.405%	$92.9139	$92.91	$92.90	$92.90
Purchase #7	$167.58	5.523%	$176.8354	$176.84	$176.85	$176.80
7 purchase totals =	$645.56		$688.1568	$688.16	$688.15	$688.20