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	$229.73	11.412%	$255.9468	$255.95	$255.95	$255.90
Purchase #2	$175.71	10.746%	$194.5918	$194.59	$194.60	$194.60
Purchase #3	$84.32	7.296%	$90.472	$90.47	$90.45	$90.50
Purchase #4	$167.98	3.308%	$173.5368	$173.54	$173.55	$173.50
Purchase #5	$38.70	12.198%	$43.4206	$43.42	$43.40	$43.40
Purchase #6	$227.33	5.592%	$240.0423	$240.04	$240.05	$240.00
Purchase #7	$69.52	11.183%	$77.2944	$77.29	$77.30	$77.30
7 purchase totals =	$993.29		$1,075.3047	$1,075.30	$1,075.30	$1,075.20