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	$166.81	11.335%	$185.7179	$185.72	$185.70	$185.70
Purchase #2	$204.59	4.417%	$213.6267	$213.63	$213.65	$213.60
Purchase #3	$115.91	13.254%	$131.2727	$131.27	$131.25	$131.30
Purchase #4	$154.31	9.558%	$169.0589	$169.06	$169.05	$169.10
Purchase #5	$171.83	5.105%	$180.6019	$180.60	$180.60	$180.60
Purchase #6	$96.65	13.626%	$109.8195	$109.82	$109.80	$109.80
Purchase #7	$97.29	10.368%	$107.377	$107.38	$107.40	$107.40
7 purchase totals =	$1,007.39		$1,097.4746	$1,097.48	$1,097.45	$1,097.50