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	$94.72	11.190%	$105.3192	$105.32	$105.30	$105.30
Purchase #2	$74.70	10.121%	$82.2604	$82.26	$82.25	$82.30
Purchase #3	$125.68	7.688%	$135.3423	$135.34	$135.35	$135.30
Purchase #4	$179.30	6.747%	$191.3974	$191.40	$191.40	$191.40
Purchase #5	$250.99	9.367%	$274.5002	$274.50	$274.50	$274.50
Purchase #6	$126.39	13.847%	$143.8912	$143.89	$143.90	$143.90
Purchase #7	$107.39	4.560%	$112.287	$112.29	$112.30	$112.30
7 purchase totals =	$959.17		$1,044.9977	$1,045.00	$1,045.00	$1,045.00