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	$98.74	4.345%	$103.0303	$103.03	$103.05	$103.00
Purchase #2	$47.97	11.180%	$53.333	$53.33	$53.35	$53.30
Purchase #3	$36.96	10.193%	$40.7273	$40.73	$40.75	$40.70
Purchase #4	$92.72	8.413%	$100.5205	$100.52	$100.50	$100.50
Purchase #5	$192.68	6.654%	$205.5009	$205.50	$205.50	$205.50
Purchase #6	$62.74	5.426%	$66.1443	$66.14	$66.15	$66.10
Purchase #7	$56.58	3.873%	$58.7713	$58.77	$58.75	$58.80
7 purchase totals =	$588.39		$628.0276	$628.02	$628.05	$627.90