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	$109.44	5.868%	$115.8619	$115.86	$115.85	$115.90
Purchase #2	$159.51	4.667%	$166.9543	$166.95	$166.95	$167.00
Purchase #3	$114.44	3.816%	$118.807	$118.81	$118.80	$118.80
Purchase #4	$202.55	6.361%	$215.4342	$215.43	$215.45	$215.40
Purchase #5	$142.39	6.230%	$151.2609	$151.26	$151.25	$151.30
Purchase #6	$38.85	9.212%	$42.4289	$42.43	$42.45	$42.40
Purchase #7	$191.53	8.524%	$207.856	$207.86	$207.85	$207.90
7 purchase totals =	$958.71		$1,018.6032	$1,018.60	$1,018.60	$1,018.70