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	$113.35	11.623%	$126.5247	$126.52	$126.50	$126.50
Purchase #2	$163.48	7.242%	$175.3192	$175.32	$175.30	$175.30
Purchase #3	$173.27	9.820%	$190.2851	$190.29	$190.30	$190.30
Purchase #4	$29.39	6.398%	$31.2704	$31.27	$31.25	$31.30
Purchase #5	$89.73	4.422%	$93.6979	$93.70	$93.70	$93.70
Purchase #6	$40.59	5.593%	$42.8602	$42.86	$42.85	$42.90
Purchase #7	$11.72	4.271%	$12.2206	$12.22	$12.20	$12.20
7 purchase totals =	$621.53		$672.1781	$672.18	$672.10	$672.20