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	$227.84	7.845%	$245.714	$245.71	$245.70	$245.70
Purchase #2	$148.87	6.288%	$158.2309	$158.23	$158.25	$158.20
Purchase #3	$109.82	5.750%	$116.1347	$116.13	$116.15	$116.10
Purchase #4	$196.89	11.725%	$219.9754	$219.98	$220.00	$220.00
Purchase #5	$111.45	6.291%	$118.4613	$118.46	$118.45	$118.50
Purchase #6	$173.64	3.543%	$179.7921	$179.79	$179.80	$179.80
Purchase #7	$190.59	3.282%	$196.8452	$196.85	$196.85	$196.80
7 purchase totals =	$1,159.10		$1,235.1536	$1,235.15	$1,235.20	$1,235.10