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	$164.37	10.598%	$181.7899	$181.79	$181.80	$181.80
Purchase #2	$19.69	9.658%	$21.5917	$21.59	$21.60	$21.60
Purchase #3	$84.56	7.148%	$90.6043	$90.60	$90.60	$90.60
Purchase #4	$51.90	8.504%	$56.3136	$56.31	$56.30	$56.30
Purchase #5	$204.65	13.346%	$231.9626	$231.96	$231.95	$232.00
Purchase #6	$204.80	12.491%	$230.3816	$230.38	$230.40	$230.40
Purchase #7	$10.80	10.386%	$11.9217	$11.92	$11.90	$11.90
7 purchase totals =	$740.77		$824.5654	$824.55	$824.55	$824.60