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	$150.67	10.620%	$166.6712	$166.67	$166.65	$166.70
Purchase #2	$72.33	12.793%	$81.5832	$81.58	$81.60	$81.60
Purchase #3	$148.47	3.838%	$154.1683	$154.17	$154.15	$154.20
Purchase #4	$80.88	13.563%	$91.8498	$91.85	$91.85	$91.80
Purchase #5	$175.52	4.467%	$183.3605	$183.36	$183.35	$183.40
Purchase #6	$178.91	9.598%	$196.0818	$196.08	$196.10	$196.10
Purchase #7	$173.98	3.771%	$180.5408	$180.54	$180.55	$180.50
7 purchase totals =	$980.76		$1,054.2556	$1,054.25	$1,054.25	$1,054.30