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	$15.71	8.310%	$17.0155	$17.02	$17.00	$17.00
Purchase #2	$150.65	5.509%	$158.9493	$158.95	$158.95	$158.90
Purchase #3	$78.94	13.204%	$89.3632	$89.36	$89.35	$89.40
Purchase #4	$132.51	9.357%	$144.909	$144.91	$144.90	$144.90
Purchase #5	$200.83	6.744%	$214.374	$214.37	$214.35	$214.40
Purchase #6	$182.27	13.446%	$206.778	$206.78	$206.80	$206.80
Purchase #7	$165.51	11.120%	$183.9147	$183.91	$183.90	$183.90
7 purchase totals =	$926.42		$1,015.3037	$1,015.30	$1,015.25	$1,015.30