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	$23.81	10.764%	$26.3729	$26.37	$26.35	$26.40
Purchase #2	$18.72	6.454%	$19.9282	$19.93	$19.95	$19.90
Purchase #3	$144.72	9.462%	$158.4134	$158.41	$158.40	$158.40
Purchase #4	$94.69	7.143%	$101.4537	$101.45	$101.45	$101.50
Purchase #5	$118.63	6.838%	$126.7419	$126.74	$126.75	$126.70
Purchase #6	$43.47	3.815%	$45.1284	$45.13	$45.15	$45.10
Purchase #7	$116.46	9.304%	$127.2954	$127.30	$127.30	$127.30
7 purchase totals =	$560.50		$605.3339	$605.33	$605.35	$605.30