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	$55.94	6.710%	$59.6936	$59.69	$59.70	$59.70
Purchase #2	$118.67	13.353%	$134.516	$134.52	$134.50	$134.50
Purchase #3	$160.66	13.308%	$182.0406	$182.04	$182.05	$182.00
Purchase #4	$176.51	11.177%	$196.2385	$196.24	$196.25	$196.20
Purchase #5	$120.44	5.468%	$127.0257	$127.03	$127.05	$127.00
Purchase #6	$163.75	3.466%	$169.4256	$169.43	$169.45	$169.40
Purchase #7	$183.55	11.749%	$205.1153	$205.12	$205.10	$205.10
7 purchase totals =	$979.52		$1,074.0553	$1,074.07	$1,074.10	$1,073.90