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	$182.71	6.330%	$194.2755	$194.28	$194.30	$194.30
Purchase #2	$174.74	12.347%	$196.3151	$196.32	$196.30	$196.30
Purchase #3	$154.63	10.136%	$170.3033	$170.30	$170.30	$170.30
Purchase #4	$58.89	6.371%	$62.6419	$62.64	$62.65	$62.60
Purchase #5	$219.66	3.841%	$228.0971	$228.10	$228.10	$228.10
Purchase #6	$138.55	4.495%	$144.7778	$144.78	$144.80	$144.80
Purchase #7	$18.57	5.525%	$19.596	$19.60	$19.60	$19.60
7 purchase totals =	$947.75		$1,016.0067	$1,016.02	$1,016.05	$1,016.00