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	$249.64	4.147%	$259.9926	$259.99	$260.00	$260.00
Purchase #2	$51.51	11.758%	$57.5665	$57.57	$57.55	$57.60
Purchase #3	$67.75	5.867%	$71.7249	$71.72	$71.70	$71.70
Purchase #4	$81.40	5.404%	$85.7989	$85.80	$85.80	$85.80
Purchase #5	$184.77	6.388%	$196.5731	$196.57	$196.55	$196.60
Purchase #6	$92.95	12.418%	$104.4925	$104.49	$104.50	$104.50
Purchase #7	$145.41	9.794%	$159.6515	$159.65	$159.65	$159.70
7 purchase totals =	$873.43		$935.8000	$935.79	$935.75	$935.90