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	$102.98	9.669%	$112.9371	$112.94	$112.95	$112.90
Purchase #2	$199.34	13.801%	$226.8509	$226.85	$226.85	$226.90
Purchase #3	$237.72	12.850%	$268.267	$268.27	$268.25	$268.30
Purchase #4	$13.95	11.873%	$15.6063	$15.61	$15.60	$15.60
Purchase #5	$133.86	6.657%	$142.7711	$142.77	$142.75	$142.80
Purchase #6	$229.31	13.621%	$260.5443	$260.54	$260.55	$260.50
Purchase #7	$71.31	10.802%	$79.0129	$79.01	$79.00	$79.00
7 purchase totals =	$988.47		$1,105.9896	$1,105.99	$1,105.95	$1,106.00