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	$182.98	12.728%	$206.2697	$206.27	$206.25	$206.30
Purchase #2	$52.44	4.504%	$54.8019	$54.80	$54.80	$54.80
Purchase #3	$195.47	9.281%	$213.6116	$213.61	$213.60	$213.60
Purchase #4	$117.58	11.300%	$130.8665	$130.87	$130.85	$130.90
Purchase #5	$155.75	6.209%	$165.4205	$165.42	$165.40	$165.40
Purchase #6	$206.30	9.317%	$225.521	$225.52	$225.50	$225.50
Purchase #7	$63.52	6.732%	$67.7962	$67.80	$67.80	$67.80
7 purchase totals =	$974.04		$1,064.2874	$1,064.29	$1,064.20	$1,064.30