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	$215.62	11.746%	$240.9467	$240.95	$240.95	$240.90
Purchase #2	$238.88	10.594%	$264.1869	$264.19	$264.20	$264.20
Purchase #3	$54.86	3.747%	$56.9156	$56.92	$56.90	$56.90
Purchase #4	$132.54	10.757%	$146.7973	$146.80	$146.80	$146.80
Purchase #5	$144.25	7.773%	$155.4626	$155.46	$155.45	$155.50
Purchase #6	$78.48	5.128%	$82.5045	$82.50	$82.50	$82.50
Purchase #7	$127.52	7.274%	$136.7958	$136.80	$136.80	$136.80
7 purchase totals =	$992.15		$1,083.6094	$1,083.62	$1,083.60	$1,083.60