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	$222.25	11.397%	$247.5798	$247.58	$247.60	$247.60
Purchase #2	$235.46	13.334%	$266.8562	$266.86	$266.85	$266.90
Purchase #3	$66.67	13.501%	$75.6711	$75.67	$75.65	$75.70
Purchase #4	$235.63	8.276%	$255.1307	$255.13	$255.15	$255.10
Purchase #5	$246.61	13.650%	$280.2723	$280.27	$280.25	$280.30
Purchase #6	$109.40	12.773%	$123.3737	$123.37	$123.35	$123.40
Purchase #7	$166.26	10.301%	$183.3864	$183.39	$183.40	$183.40
7 purchase totals =	$1,282.28		$1,432.2702	$1,432.27	$1,432.25	$1,432.40