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	$136.93	10.807%	$151.728	$151.73	$151.75	$151.70
Purchase #2	$174.27	10.567%	$192.6851	$192.69	$192.70	$192.70
Purchase #3	$249.39	13.301%	$282.5614	$282.56	$282.55	$282.60
Purchase #4	$74.51	5.737%	$78.7846	$78.78	$78.80	$78.80
Purchase #5	$134.91	5.243%	$141.9833	$141.98	$142.00	$142.00
Purchase #6	$176.82	4.526%	$184.8229	$184.82	$184.80	$184.80
Purchase #7	$33.36	3.848%	$34.6437	$34.64	$34.65	$34.60
7 purchase totals =	$980.19		$1,067.2090	$1,067.20	$1,067.25	$1,067.20