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	$141.78	6.794%	$151.4125	$151.41	$151.40	$151.40
Purchase #2	$9.90	4.850%	$10.3802	$10.38	$10.40	$10.40
Purchase #3	$56.51	5.549%	$59.6457	$59.65	$59.65	$59.60
Purchase #4	$176.54	6.236%	$187.549	$187.55	$187.55	$187.50
Purchase #5	$190.29	13.416%	$215.8193	$215.82	$215.80	$215.80
Purchase #6	$146.44	11.331%	$163.0331	$163.03	$163.05	$163.00
Purchase #7	$187.97	4.589%	$196.5959	$196.60	$196.60	$196.60
7 purchase totals =	$909.43		$984.4357	$984.44	$984.45	$984.30