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	$105.29	8.857%	$114.6155	$114.62	$114.60	$114.60
Purchase #2	$51.88	6.773%	$55.3938	$55.39	$55.40	$55.40
Purchase #3	$52.49	9.360%	$57.4031	$57.40	$57.40	$57.40
Purchase #4	$94.39	8.431%	$102.348	$102.35	$102.35	$102.30
Purchase #5	$82.78	8.202%	$89.5696	$89.57	$89.55	$89.60
Purchase #6	$150.69	6.278%	$160.1503	$160.15	$160.15	$160.20
Purchase #7	$120.54	4.594%	$126.0776	$126.08	$126.10	$126.10
7 purchase totals =	$658.06		$705.5579	$705.56	$705.55	$705.60