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	$217.82	11.475%	$242.8148	$242.81	$242.80	$242.80
Purchase #2	$68.88	12.499%	$77.4893	$77.49	$77.50	$77.50
Purchase #3	$25.51	8.196%	$27.6008	$27.60	$27.60	$27.60
Purchase #4	$145.70	4.515%	$152.2784	$152.28	$152.30	$152.30
Purchase #5	$145.42	10.145%	$160.1729	$160.17	$160.15	$160.20
Purchase #6	$102.63	3.108%	$105.8197	$105.82	$105.80	$105.80
Purchase #7	$7.43	6.580%	$7.9189	$7.92	$7.90	$7.90
7 purchase totals =	$713.39		$774.0948	$774.09	$774.05	$774.10