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	$60.42	3.309%	$62.4193	$62.42	$62.40	$62.40
Purchase #2	$124.96	11.870%	$139.7928	$139.79	$139.80	$139.80
Purchase #3	$219.83	10.150%	$242.1427	$242.14	$242.15	$242.10
Purchase #4	$100.87	13.621%	$114.6095	$114.61	$114.60	$114.60
Purchase #5	$132.92	6.594%	$141.6847	$141.68	$141.70	$141.70
Purchase #6	$142.60	6.771%	$152.2554	$152.26	$152.25	$152.30
Purchase #7	$188.86	5.309%	$198.8866	$198.89	$198.90	$198.90
7 purchase totals =	$970.46		$1,051.7910	$1,051.79	$1,051.80	$1,051.80