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	$178.50	10.516%	$197.2711	$197.27	$197.25	$197.30
Purchase #2	$148.70	6.118%	$157.7975	$157.80	$157.80	$157.80
Purchase #3	$109.84	12.466%	$123.5327	$123.53	$123.55	$123.50
Purchase #4	$43.39	10.110%	$47.7767	$47.78	$47.80	$47.80
Purchase #5	$137.80	5.504%	$145.3845	$145.38	$145.40	$145.40
Purchase #6	$101.46	11.833%	$113.4658	$113.47	$113.45	$113.50
Purchase #7	$74.91	4.498%	$78.2795	$78.28	$78.30	$78.30
7 purchase totals =	$794.60		$863.5078	$863.51	$863.55	$863.60