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	$191.89	7.756%	$206.773	$206.77	$206.75	$206.80
Purchase #2	$164.29	4.130%	$171.0752	$171.08	$171.10	$171.10
Purchase #3	$113.79	13.326%	$128.9537	$128.95	$128.95	$129.00
Purchase #4	$82.80	10.648%	$91.6165	$91.62	$91.60	$91.60
Purchase #5	$105.28	7.103%	$112.758	$112.76	$112.75	$112.80
Purchase #6	$138.63	4.491%	$144.8559	$144.86	$144.85	$144.90
Purchase #7	$12.93	10.655%	$14.3077	$14.31	$14.30	$14.30
7 purchase totals =	$809.61		$870.3400	$870.35	$870.30	$870.50