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	$79.86	4.478%	$83.4361	$83.44	$83.45	$83.40
Purchase #2	$95.37	10.773%	$105.6442	$105.64	$105.65	$105.60
Purchase #3	$148.86	12.761%	$167.856	$167.86	$167.85	$167.90
Purchase #4	$114.27	10.345%	$126.0912	$126.09	$126.10	$126.10
Purchase #5	$162.49	12.478%	$182.7655	$182.77	$182.75	$182.80
Purchase #6	$103.94	5.450%	$109.6047	$109.60	$109.60	$109.60
Purchase #7	$159.80	12.715%	$180.1186	$180.12	$180.10	$180.10
7 purchase totals =	$864.59		$955.5163	$955.52	$955.50	$955.50