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	$174.71	7.857%	$188.437	$188.44	$188.45	$188.40
Purchase #2	$220.85	7.772%	$238.0145	$238.01	$238.00	$238.00
Purchase #3	$133.58	5.730%	$141.2341	$141.23	$141.25	$141.20
Purchase #4	$116.99	11.576%	$130.5328	$130.53	$130.55	$130.50
Purchase #5	$99.64	11.758%	$111.3557	$111.36	$111.35	$111.40
Purchase #6	$116.27	10.415%	$128.3795	$128.38	$128.40	$128.40
Purchase #7	$197.98	8.643%	$215.0914	$215.09	$215.10	$215.10
7 purchase totals =	$1,060.02		$1,153.0450	$1,153.04	$1,153.10	$1,153.00