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	$47.92	13.763%	$54.5152	$54.52	$54.50	$54.50
Purchase #2	$67.46	10.750%	$74.712	$74.71	$74.70	$74.70
Purchase #3	$54.64	3.564%	$56.5874	$56.59	$56.60	$56.60
Purchase #4	$217.82	8.760%	$236.901	$236.90	$236.90	$236.90
Purchase #5	$41.77	9.419%	$45.7043	$45.70	$45.70	$45.70
Purchase #6	$73.60	6.874%	$78.6593	$78.66	$78.65	$78.70
Purchase #7	$74.65	8.647%	$81.105	$81.11	$81.10	$81.10
7 purchase totals =	$577.86		$628.1842	$628.19	$628.15	$628.20