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	$41.55	13.446%	$47.1368	$47.14	$47.15	$47.10
Purchase #2	$121.39	5.633%	$128.2279	$128.23	$128.25	$128.20
Purchase #3	$185.31	4.708%	$194.0344	$194.03	$194.05	$194.00
Purchase #4	$132.64	3.201%	$136.8858	$136.89	$136.90	$136.90
Purchase #5	$105.47	6.364%	$112.1821	$112.18	$112.20	$112.20
Purchase #6	$164.77	9.578%	$180.5517	$180.55	$180.55	$180.60
Purchase #7	$126.74	6.113%	$134.4876	$134.49	$134.50	$134.50
7 purchase totals =	$877.87		$933.5063	$933.51	$933.60	$933.50