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	$13.90	7.298%	$14.9144	$14.91	$14.90	$14.90
Purchase #2	$99.25	12.322%	$111.4796	$111.48	$111.50	$111.50
Purchase #3	$129.41	10.578%	$143.099	$143.10	$143.10	$143.10
Purchase #4	$248.68	13.209%	$281.5281	$281.53	$281.55	$281.50
Purchase #5	$238.91	12.528%	$268.8406	$268.84	$268.85	$268.80
Purchase #6	$70.39	5.186%	$74.0404	$74.04	$74.05	$74.00
Purchase #7	$104.80	13.176%	$118.6084	$118.61	$118.60	$118.60
7 purchase totals =	$905.34		$1,012.5105	$1,012.51	$1,012.55	$1,012.40