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	$221.89	8.389%	$240.5044	$240.50	$240.50	$240.50
Purchase #2	$240.47	11.677%	$268.5497	$268.55	$268.55	$268.50
Purchase #3	$52.57	4.568%	$54.9714	$54.97	$54.95	$55.00
Purchase #4	$20.34	13.846%	$23.1563	$23.16	$23.15	$23.20
Purchase #5	$199.72	11.389%	$222.4661	$222.47	$222.45	$222.50
Purchase #6	$122.35	5.103%	$128.5935	$128.59	$128.60	$128.60
Purchase #7	$154.28	3.108%	$159.075	$159.08	$159.10	$159.10
7 purchase totals =	$1,011.62		$1,097.3164	$1,097.32	$1,097.30	$1,097.40