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	$207.55	3.185%	$214.1605	$214.16	$214.15	$214.20
Purchase #2	$141.91	13.507%	$161.0778	$161.08	$161.10	$161.10
Purchase #3	$131.62	3.852%	$136.69	$136.69	$136.70	$136.70
Purchase #4	$80.86	11.275%	$89.977	$89.98	$90.00	$90.00
Purchase #5	$134.29	7.685%	$144.6102	$144.61	$144.60	$144.60
Purchase #6	$221.77	13.492%	$251.6912	$251.69	$251.70	$251.70
Purchase #7	$183.33	8.198%	$198.3594	$198.36	$198.35	$198.40
7 purchase totals =	$1,101.33		$1,196.5661	$1,196.57	$1,196.60	$1,196.70