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	$144.63	11.622%	$161.4389	$161.44	$161.45	$161.40
Purchase #2	$169.31	4.109%	$176.2669	$176.27	$176.25	$176.30
Purchase #3	$47.38	11.447%	$52.8036	$52.80	$52.80	$52.80
Purchase #4	$109.29	8.105%	$118.148	$118.15	$118.15	$118.10
Purchase #5	$105.76	12.804%	$119.3015	$119.30	$119.30	$119.30
Purchase #6	$91.42	10.407%	$100.9341	$100.93	$100.95	$100.90
Purchase #7	$216.74	7.832%	$233.7151	$233.72	$233.70	$233.70
7 purchase totals =	$884.53		$962.6081	$962.61	$962.60	$962.50