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	$53.40	4.746%	$55.9344	$55.93	$55.95	$55.90
Purchase #2	$53.40	5.286%	$56.2227	$56.22	$56.20	$56.20
Purchase #3	$69.71	5.460%	$73.5162	$73.52	$73.50	$73.50
Purchase #4	$107.34	4.691%	$112.3753	$112.38	$112.40	$112.40
Purchase #5	$52.31	4.542%	$54.6859	$54.69	$54.70	$54.70
Purchase #6	$151.86	13.260%	$171.9966	$172.00	$172.00	$172.00
Purchase #7	$244.39	7.801%	$263.4549	$263.45	$263.45	$263.50
7 purchase totals =	$732.41		$788.1860	$788.19	$788.20	$788.20