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	$234.93	8.208%	$254.2131	$254.21	$254.20	$254.20
Purchase #2	$145.76	6.281%	$154.9152	$154.92	$154.90	$154.90
Purchase #3	$180.57	11.275%	$200.9293	$200.93	$200.95	$200.90
Purchase #4	$155.75	10.490%	$172.0882	$172.09	$172.10	$172.10
Purchase #5	$43.98	10.174%	$48.4545	$48.45	$48.45	$48.50
Purchase #6	$36.58	10.590%	$40.4538	$40.45	$40.45	$40.50
Purchase #7	$189.52	13.720%	$215.5221	$215.52	$215.50	$215.50
7 purchase totals =	$987.09		$1,086.5762	$1,086.57	$1,086.55	$1,086.60