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	$57.51	9.161%	$62.7785	$62.78	$62.80	$62.80
Purchase #2	$161.32	4.300%	$168.2568	$168.26	$168.25	$168.30
Purchase #3	$128.41	12.743%	$144.7733	$144.77	$144.75	$144.80
Purchase #4	$73.27	12.189%	$82.2009	$82.20	$82.20	$82.20
Purchase #5	$6.28	3.833%	$6.5207	$6.52	$6.50	$6.50
Purchase #6	$215.62	3.172%	$222.4595	$222.46	$222.45	$222.50
Purchase #7	$8.89	7.784%	$9.582	$9.58	$9.60	$9.60
7 purchase totals =	$651.30		$696.5717	$696.57	$696.55	$696.70