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	$119.42	3.515%	$123.6176	$123.62	$123.60	$123.60
Purchase #2	$118.50	5.215%	$124.6798	$124.68	$124.70	$124.70
Purchase #3	$38.75	11.440%	$43.183	$43.18	$43.20	$43.20
Purchase #4	$234.72	9.325%	$256.6076	$256.61	$256.60	$256.60
Purchase #5	$14.45	5.734%	$15.2786	$15.28	$15.30	$15.30
Purchase #6	$142.86	3.758%	$148.2287	$148.23	$148.25	$148.20
Purchase #7	$249.75	10.242%	$275.3294	$275.33	$275.35	$275.30
7 purchase totals =	$918.45		$986.9247	$986.93	$987.00	$986.90