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	$170.78	13.828%	$194.3955	$194.40	$194.40	$194.40
Purchase #2	$197.81	6.808%	$211.2769	$211.28	$211.30	$211.30
Purchase #3	$179.70	9.123%	$196.094	$196.09	$196.10	$196.10
Purchase #4	$120.96	6.444%	$128.7547	$128.75	$128.75	$128.80
Purchase #5	$118.49	6.372%	$126.0402	$126.04	$126.05	$126.00
Purchase #6	$38.75	12.601%	$43.6329	$43.63	$43.65	$43.60
Purchase #7	$36.52	10.244%	$40.2611	$40.26	$40.25	$40.30
7 purchase totals =	$863.01		$940.4553	$940.45	$940.50	$940.50