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	$241.56	10.500%	$266.9238	$266.92	$266.90	$266.90
Purchase #2	$49.87	10.780%	$55.246	$55.25	$55.25	$55.20
Purchase #3	$87.41	13.745%	$99.4245	$99.42	$99.40	$99.40
Purchase #4	$52.81	13.794%	$60.0946	$60.09	$60.10	$60.10
Purchase #5	$124.39	5.661%	$131.4317	$131.43	$131.45	$131.40
Purchase #6	$85.45	12.455%	$96.0928	$96.09	$96.10	$96.10
Purchase #7	$13.55	13.474%	$15.3757	$15.38	$15.40	$15.40
7 purchase totals =	$655.04		$724.5891	$724.58	$724.60	$724.50