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	$101.33	7.863%	$109.2976	$109.30	$109.30	$109.30
Purchase #2	$165.59	12.670%	$186.5703	$186.57	$186.55	$186.60
Purchase #3	$119.55	10.458%	$132.0525	$132.05	$132.05	$132.10
Purchase #4	$163.30	6.417%	$173.779	$173.78	$173.80	$173.80
Purchase #5	$173.30	9.692%	$190.0962	$190.10	$190.10	$190.10
Purchase #6	$180.51	7.501%	$194.0501	$194.05	$194.05	$194.10
Purchase #7	$113.35	12.395%	$127.3997	$127.40	$127.40	$127.40
7 purchase totals =	$1,016.93		$1,113.2454	$1,113.25	$1,113.25	$1,113.40