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	$158.35	3.646%	$164.1234	$164.12	$164.10	$164.10
Purchase #2	$110.77	6.845%	$118.3522	$118.35	$118.35	$118.40
Purchase #3	$67.25	6.569%	$71.6677	$71.67	$71.65	$71.70
Purchase #4	$174.53	7.299%	$187.2689	$187.27	$187.25	$187.30
Purchase #5	$153.27	3.278%	$158.2942	$158.29	$158.30	$158.30
Purchase #6	$237.65	10.311%	$262.1541	$262.15	$262.15	$262.20
Purchase #7	$60.51	11.812%	$67.6574	$67.66	$67.65	$67.70
7 purchase totals =	$962.33		$1,029.5179	$1,029.51	$1,029.45	$1,029.70