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	$40.67	13.432%	$46.1328	$46.13	$46.15	$46.10
Purchase #2	$241.87	11.262%	$269.1094	$269.11	$269.10	$269.10
Purchase #3	$194.26	10.761%	$215.1643	$215.16	$215.15	$215.20
Purchase #4	$139.76	12.398%	$157.0874	$157.09	$157.10	$157.10
Purchase #5	$78.75	12.346%	$88.4725	$88.47	$88.45	$88.50
Purchase #6	$40.98	6.770%	$43.7543	$43.75	$43.75	$43.80
Purchase #7	$231.50	4.565%	$242.068	$242.07	$242.05	$242.10
7 purchase totals =	$967.79		$1,061.7887	$1,061.78	$1,061.75	$1,061.90