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	$128.80	4.420%	$134.493	$134.49	$134.50	$134.50
Purchase #2	$59.69	6.601%	$63.6301	$63.63	$63.65	$63.60
Purchase #3	$146.77	8.659%	$159.4788	$159.48	$159.50	$159.50
Purchase #4	$121.50	12.432%	$136.6049	$136.60	$136.60	$136.60
Purchase #5	$248.30	13.774%	$282.5008	$282.50	$282.50	$282.50
Purchase #6	$248.92	11.128%	$276.6198	$276.62	$276.60	$276.60
Purchase #7	$37.50	12.161%	$42.0604	$42.06	$42.05	$42.10
7 purchase totals =	$991.48		$1,095.3878	$1,095.38	$1,095.40	$1,095.40