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	$213.78	11.481%	$238.3241	$238.32	$238.30	$238.30
Purchase #2	$146.52	5.127%	$154.0321	$154.03	$154.05	$154.00
Purchase #3	$54.53	8.362%	$59.0898	$59.09	$59.10	$59.10
Purchase #4	$105.84	12.215%	$118.7684	$118.77	$118.75	$118.80
Purchase #5	$12.59	9.302%	$13.7611	$13.76	$13.75	$13.80
Purchase #6	$103.74	5.140%	$109.0722	$109.07	$109.05	$109.10
Purchase #7	$84.80	11.773%	$94.7835	$94.78	$94.80	$94.80
7 purchase totals =	$721.80		$787.8312	$787.82	$787.80	$787.90