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	$70.89	11.333%	$78.924	$78.92	$78.90	$78.90
Purchase #2	$47.44	13.536%	$53.8615	$53.86	$53.85	$53.90
Purchase #3	$238.88	3.219%	$246.5695	$246.57	$246.55	$246.60
Purchase #4	$159.43	10.764%	$176.591	$176.59	$176.60	$176.60
Purchase #5	$54.81	3.337%	$56.639	$56.64	$56.65	$56.60
Purchase #6	$58.93	8.414%	$63.8884	$63.89	$63.90	$63.90
Purchase #7	$105.32	12.278%	$118.2512	$118.25	$118.25	$118.30
7 purchase totals =	$735.70		$794.7246	$794.72	$794.70	$794.80