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	$161.27	12.150%	$180.8643	$180.86	$180.85	$180.90
Purchase #2	$175.40	5.254%	$184.6155	$184.62	$184.60	$184.60
Purchase #3	$215.38	12.264%	$241.7942	$241.79	$241.80	$241.80
Purchase #4	$200.61	9.575%	$219.8184	$219.82	$219.80	$219.80
Purchase #5	$9.46	11.180%	$10.5176	$10.52	$10.50	$10.50
Purchase #6	$178.77	9.671%	$196.0588	$196.06	$196.05	$196.10
Purchase #7	$16.35	11.673%	$18.2585	$18.26	$18.25	$18.30
7 purchase totals =	$957.24		$1,051.9273	$1,051.93	$1,051.85	$1,052.00