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	$97.76	5.536%	$103.172	$103.17	$103.15	$103.20
Purchase #2	$132.28	10.867%	$146.6549	$146.65	$146.65	$146.70
Purchase #3	$179.65	9.499%	$196.715	$196.72	$196.70	$196.70
Purchase #4	$195.46	5.798%	$206.7928	$206.79	$206.80	$206.80
Purchase #5	$12.78	10.357%	$14.1036	$14.10	$14.10	$14.10
Purchase #6	$45.43	13.621%	$51.618	$51.62	$51.60	$51.60
Purchase #7	$84.47	4.704%	$88.4435	$88.44	$88.45	$88.40
7 purchase totals =	$747.83		$807.4998	$807.49	$807.45	$807.50