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	$111.93	6.150%	$118.8137	$118.81	$118.80	$118.80
Purchase #2	$25.36	6.521%	$27.0137	$27.01	$27.00	$27.00
Purchase #3	$62.52	4.777%	$65.5066	$65.51	$65.50	$65.50
Purchase #4	$56.27	11.468%	$62.723	$62.72	$62.70	$62.70
Purchase #5	$38.60	13.138%	$43.6713	$43.67	$43.65	$43.70
Purchase #6	$26.74	6.570%	$28.4968	$28.50	$28.50	$28.50
Purchase #7	$158.44	7.497%	$170.3182	$170.32	$170.30	$170.30
7 purchase totals =	$479.86		$516.5433	$516.54	$516.45	$516.50