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	$151.53	4.822%	$158.8368	$158.84	$158.85	$158.80
Purchase #2	$51.93	5.109%	$54.5831	$54.58	$54.60	$54.60
Purchase #3	$93.28	9.672%	$102.302	$102.30	$102.30	$102.30
Purchase #4	$79.28	10.143%	$87.3214	$87.32	$87.30	$87.30
Purchase #5	$94.43	5.238%	$99.3762	$99.38	$99.40	$99.40
Purchase #6	$23.30	4.686%	$24.3918	$24.39	$24.40	$24.40
Purchase #7	$30.60	3.422%	$31.6471	$31.65	$31.65	$31.60
7 purchase totals =	$524.35		$558.4584	$558.46	$558.50	$558.40