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	$12.69	9.763%	$13.9289	$13.93	$13.95	$13.90
Purchase #2	$234.76	3.305%	$242.5188	$242.52	$242.50	$242.50
Purchase #3	$186.29	4.456%	$194.5911	$194.59	$194.60	$194.60
Purchase #4	$82.81	10.506%	$91.51	$91.51	$91.50	$91.50
Purchase #5	$124.83	7.693%	$134.4332	$134.43	$134.45	$134.40
Purchase #6	$84.72	8.179%	$91.6492	$91.65	$91.65	$91.60
Purchase #7	$146.46	13.798%	$166.6686	$166.67	$166.65	$166.70
7 purchase totals =	$872.56		$935.2998	$935.30	$935.30	$935.20