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	$242.73	10.110%	$267.27	$267.27	$267.25	$267.30
Purchase #2	$17.51	13.335%	$19.845	$19.85	$19.85	$19.80
Purchase #3	$77.61	8.153%	$83.9375	$83.94	$83.95	$83.90
Purchase #4	$36.75	5.113%	$38.629	$38.63	$38.65	$38.60
Purchase #5	$102.27	8.614%	$111.0795	$111.08	$111.10	$111.10
Purchase #6	$29.28	8.481%	$31.7632	$31.76	$31.75	$31.80
Purchase #7	$120.85	6.458%	$128.6545	$128.65	$128.65	$128.70
7 purchase totals =	$627.00		$681.1787	$681.18	$681.20	$681.20