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	$156.61	9.554%	$171.5725	$171.57	$171.55	$171.60
Purchase #2	$47.41	13.793%	$53.9493	$53.95	$53.95	$53.90
Purchase #3	$234.78	5.521%	$247.7422	$247.74	$247.75	$247.70
Purchase #4	$111.38	13.653%	$126.5867	$126.59	$126.60	$126.60
Purchase #5	$245.42	4.782%	$257.156	$257.16	$257.15	$257.20
Purchase #6	$92.49	8.838%	$100.6643	$100.66	$100.65	$100.70
Purchase #7	$161.86	13.628%	$183.9183	$183.92	$183.90	$183.90
7 purchase totals =	$1,049.95		$1,141.5893	$1,141.59	$1,141.55	$1,141.60