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	$81.98	8.846%	$89.232	$89.23	$89.25	$89.20
Purchase #2	$39.72	13.838%	$45.2165	$45.22	$45.20	$45.20
Purchase #3	$47.61	7.251%	$51.0622	$51.06	$51.05	$51.10
Purchase #4	$237.87	4.401%	$248.3387	$248.34	$248.35	$248.30
Purchase #5	$77.80	4.820%	$81.55	$81.55	$81.55	$81.60
Purchase #6	$237.64	7.255%	$254.8808	$254.88	$254.90	$254.90
Purchase #7	$38.32	12.613%	$43.1533	$43.15	$43.15	$43.20
7 purchase totals =	$760.94		$813.4335	$813.43	$813.45	$813.50