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	$162.53	4.653%	$170.0925	$170.09	$170.10	$170.10
Purchase #2	$112.90	7.145%	$120.9667	$120.97	$120.95	$121.00
Purchase #3	$33.79	11.207%	$37.5768	$37.58	$37.60	$37.60
Purchase #4	$173.55	12.238%	$194.789	$194.79	$194.80	$194.80
Purchase #5	$113.29	12.474%	$127.4218	$127.42	$127.40	$127.40
Purchase #6	$111.43	10.763%	$123.4232	$123.42	$123.40	$123.40
Purchase #7	$138.59	12.771%	$156.2893	$156.29	$156.30	$156.30
7 purchase totals =	$846.08		$930.5593	$930.56	$930.55	$930.60