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	$226.75	9.798%	$248.967	$248.97	$248.95	$249.00
Purchase #2	$167.38	6.718%	$178.6246	$178.62	$178.60	$178.60
Purchase #3	$128.25	13.707%	$145.8292	$145.83	$145.85	$145.80
Purchase #4	$114.65	12.216%	$128.6556	$128.66	$128.65	$128.70
Purchase #5	$51.35	6.301%	$54.5856	$54.59	$54.60	$54.60
Purchase #6	$184.25	5.164%	$193.7647	$193.76	$193.75	$193.80
Purchase #7	$146.72	10.427%	$162.0185	$162.02	$162.00	$162.00
7 purchase totals =	$1,019.35		$1,112.4452	$1,112.45	$1,112.40	$1,112.50