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	$96.69	9.149%	$105.5362	$105.54	$105.55	$105.50
Purchase #2	$181.58	13.543%	$206.1714	$206.17	$206.15	$206.20
Purchase #3	$39.33	11.464%	$43.8388	$43.84	$43.85	$43.80
Purchase #4	$244.67	4.540%	$255.778	$255.78	$255.80	$255.80
Purchase #5	$101.74	5.863%	$107.705	$107.71	$107.70	$107.70
Purchase #6	$180.59	13.557%	$205.0726	$205.07	$205.05	$205.10
Purchase #7	$122.35	7.765%	$131.8505	$131.85	$131.85	$131.90
7 purchase totals =	$966.95		$1,055.9525	$1,055.96	$1,055.95	$1,056.00