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	$90.58	7.710%	$97.5637	$97.56	$97.55	$97.60
Purchase #2	$18.29	9.798%	$20.0821	$20.08	$20.10	$20.10
Purchase #3	$115.87	13.170%	$131.1301	$131.13	$131.15	$131.10
Purchase #4	$100.81	9.676%	$110.5644	$110.56	$110.55	$110.60
Purchase #5	$132.71	8.676%	$144.2239	$144.22	$144.20	$144.20
Purchase #6	$10.69	8.651%	$11.6148	$11.61	$11.60	$11.60
Purchase #7	$174.59	3.263%	$180.2869	$180.29	$180.30	$180.30
7 purchase totals =	$643.54		$695.4659	$695.45	$695.45	$695.50