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	$85.52	4.573%	$89.4308	$89.43	$89.45	$89.40
Purchase #2	$32.57	7.698%	$35.0772	$35.08	$35.10	$35.10
Purchase #3	$88.92	13.179%	$100.6388	$100.64	$100.65	$100.60
Purchase #4	$74.37	10.381%	$82.0903	$82.09	$82.10	$82.10
Purchase #5	$96.37	7.453%	$103.5525	$103.55	$103.55	$103.60
Purchase #6	$239.28	10.196%	$263.677	$263.68	$263.70	$263.70
Purchase #7	$38.81	6.626%	$41.3816	$41.38	$41.40	$41.40
7 purchase totals =	$655.84		$715.8482	$715.85	$715.95	$715.90