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	$144.58	5.175%	$152.062	$152.06	$152.05	$152.10
Purchase #2	$55.38	12.287%	$62.1845	$62.18	$62.20	$62.20
Purchase #3	$89.25	11.187%	$99.2344	$99.23	$99.25	$99.20
Purchase #4	$88.36	13.172%	$99.9988	$100.00	$100.00	$100.00
Purchase #5	$97.78	5.118%	$102.7844	$102.78	$102.80	$102.80
Purchase #6	$17.39	8.384%	$18.848	$18.85	$18.85	$18.80
Purchase #7	$93.88	12.475%	$105.5915	$105.59	$105.60	$105.60
7 purchase totals =	$586.62		$640.7036	$640.69	$640.75	$640.70