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	$43.64	4.255%	$45.4969	$45.50	$45.50	$45.50
Purchase #2	$138.94	6.622%	$148.1406	$148.14	$148.15	$148.10
Purchase #3	$40.89	5.423%	$43.1075	$43.11	$43.10	$43.10
Purchase #4	$59.27	3.469%	$61.3261	$61.33	$61.35	$61.30
Purchase #5	$220.60	8.487%	$239.3223	$239.32	$239.30	$239.30
Purchase #6	$11.44	13.148%	$12.9441	$12.94	$12.95	$12.90
Purchase #7	$201.93	10.655%	$223.4456	$223.45	$223.45	$223.40
7 purchase totals =	$716.71		$773.7831	$773.79	$773.80	$773.60