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	$130.50	6.748%	$139.3061	$139.31	$139.30	$139.30
Purchase #2	$44.99	11.700%	$50.2538	$50.25	$50.25	$50.30
Purchase #3	$147.48	4.538%	$154.1726	$154.17	$154.15	$154.20
Purchase #4	$232.25	13.156%	$262.8048	$262.80	$262.80	$262.80
Purchase #5	$121.45	4.630%	$127.0731	$127.07	$127.05	$127.10
Purchase #6	$201.75	13.428%	$228.841	$228.84	$228.85	$228.80
Purchase #7	$51.85	3.379%	$53.602	$53.60	$53.60	$53.60
7 purchase totals =	$930.27		$1,016.0534	$1,016.04	$1,016.00	$1,016.10