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	$224.38	12.202%	$251.7588	$251.76	$251.75	$251.80
Purchase #2	$107.77	10.678%	$119.2777	$119.28	$119.30	$119.30
Purchase #3	$83.26	3.203%	$85.9268	$85.93	$85.95	$85.90
Purchase #4	$217.83	10.515%	$240.7348	$240.73	$240.75	$240.70
Purchase #5	$116.43	6.415%	$123.899	$123.90	$123.90	$123.90
Purchase #6	$180.89	10.598%	$200.0607	$200.06	$200.05	$200.10
Purchase #7	$241.48	10.497%	$266.8282	$266.83	$266.85	$266.80
7 purchase totals =	$1,172.04		$1,288.4860	$1,288.49	$1,288.55	$1,288.50