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	$165.25	6.760%	$176.4209	$176.42	$176.40	$176.40
Purchase #2	$194.62	5.701%	$205.7153	$205.72	$205.70	$205.70
Purchase #3	$85.33	8.485%	$92.5703	$92.57	$92.55	$92.60
Purchase #4	$102.42	4.801%	$107.3372	$107.34	$107.35	$107.30
Purchase #5	$138.89	13.778%	$158.0263	$158.03	$158.05	$158.00
Purchase #6	$119.43	6.686%	$127.4151	$127.42	$127.40	$127.40
Purchase #7	$51.28	8.243%	$55.507	$55.51	$55.50	$55.50
7 purchase totals =	$857.22		$922.9921	$923.01	$922.95	$922.90