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	$10.87	5.409%	$11.458	$11.46	$11.45	$11.50
Purchase #2	$223.86	10.631%	$247.6586	$247.66	$247.65	$247.70
Purchase #3	$239.38	11.541%	$267.0068	$267.01	$267.00	$267.00
Purchase #4	$187.72	4.820%	$196.7681	$196.77	$196.75	$196.80
Purchase #5	$195.39	12.558%	$219.9271	$219.93	$219.95	$219.90
Purchase #6	$174.84	7.239%	$187.4967	$187.50	$187.50	$187.50
Purchase #7	$152.98	9.365%	$167.3066	$167.31	$167.30	$167.30
7 purchase totals =	$1,185.04		$1,297.6219	$1,297.64	$1,297.60	$1,297.70