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	$78.93	10.117%	$86.9153	$86.92	$86.90	$86.90
Purchase #2	$68.85	5.526%	$72.6547	$72.65	$72.65	$72.70
Purchase #3	$69.72	4.354%	$72.7556	$72.76	$72.75	$72.80
Purchase #4	$49.40	8.631%	$53.6637	$53.66	$53.65	$53.70
Purchase #5	$185.58	12.258%	$208.3284	$208.33	$208.35	$208.30
Purchase #6	$9.46	11.252%	$10.5244	$10.52	$10.50	$10.50
Purchase #7	$63.90	13.859%	$72.7559	$72.76	$72.75	$72.80
7 purchase totals =	$525.84		$577.5980	$577.60	$577.55	$577.70