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	$227.71	13.844%	$259.2342	$259.23	$259.25	$259.20
Purchase #2	$53.95	12.828%	$60.8707	$60.87	$60.85	$60.90
Purchase #3	$113.52	8.867%	$123.5858	$123.59	$123.60	$123.60
Purchase #4	$156.33	11.256%	$173.9265	$173.93	$173.95	$173.90
Purchase #5	$188.77	4.204%	$196.7059	$196.71	$196.70	$196.70
Purchase #6	$216.42	13.267%	$245.1324	$245.13	$245.15	$245.10
Purchase #7	$14.71	4.543%	$15.3783	$15.38	$15.40	$15.40
7 purchase totals =	$971.41		$1,074.8338	$1,074.84	$1,074.90	$1,074.80