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	$193.59	11.329%	$215.5218	$215.52	$215.50	$215.50
Purchase #2	$178.66	8.594%	$194.014	$194.01	$194.00	$194.00
Purchase #3	$224.62	5.108%	$236.0936	$236.09	$236.10	$236.10
Purchase #4	$154.66	11.537%	$172.5031	$172.50	$172.50	$172.50
Purchase #5	$77.39	7.106%	$82.8893	$82.89	$82.90	$82.90
Purchase #6	$154.54	5.110%	$162.437	$162.44	$162.45	$162.40
Purchase #7	$119.64	6.394%	$127.2898	$127.29	$127.30	$127.30
7 purchase totals =	$1,103.10		$1,190.7486	$1,190.74	$1,190.75	$1,190.70