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	$217.88	9.478%	$238.5307	$238.53	$238.55	$238.50
Purchase #2	$45.86	6.746%	$48.9537	$48.95	$48.95	$49.00
Purchase #3	$164.95	3.838%	$171.2808	$171.28	$171.30	$171.30
Purchase #4	$65.48	12.870%	$73.9073	$73.91	$73.90	$73.90
Purchase #5	$102.55	8.398%	$111.1621	$111.16	$111.15	$111.20
Purchase #6	$178.69	4.695%	$187.0795	$187.08	$187.10	$187.10
Purchase #7	$124.89	10.784%	$138.3581	$138.36	$138.35	$138.40
7 purchase totals =	$900.30		$969.2722	$969.27	$969.30	$969.40