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	$121.85	7.860%	$131.4274	$131.43	$131.45	$131.40
Purchase #2	$52.47	7.740%	$56.5312	$56.53	$56.55	$56.50
Purchase #3	$49.62	6.519%	$52.8547	$52.85	$52.85	$52.90
Purchase #4	$183.74	3.615%	$190.3822	$190.38	$190.40	$190.40
Purchase #5	$55.85	8.204%	$60.4319	$60.43	$60.45	$60.40
Purchase #6	$62.41	6.706%	$66.5952	$66.60	$66.60	$66.60
Purchase #7	$60.75	10.534%	$67.1494	$67.15	$67.15	$67.10
7 purchase totals =	$586.69		$625.3720	$625.37	$625.45	$625.30