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	$154.83	3.488%	$160.2305	$160.23	$160.25	$160.20
Purchase #2	$242.51	11.259%	$269.8142	$269.81	$269.80	$269.80
Purchase #3	$97.93	13.748%	$111.3934	$111.39	$111.40	$111.40
Purchase #4	$154.38	13.323%	$174.948	$174.95	$174.95	$174.90
Purchase #5	$35.46	8.455%	$38.4581	$38.46	$38.45	$38.50
Purchase #6	$121.90	4.501%	$127.3867	$127.39	$127.40	$127.40
Purchase #7	$61.67	3.242%	$63.6693	$63.67	$63.65	$63.70
7 purchase totals =	$868.68		$945.9002	$945.90	$945.90	$945.90