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	$41.83	10.765%	$46.333	$46.33	$46.35	$46.30
Purchase #2	$208.57	9.254%	$227.8711	$227.87	$227.85	$227.90
Purchase #3	$85.33	4.199%	$88.913	$88.91	$88.90	$88.90
Purchase #4	$166.86	10.224%	$183.9198	$183.92	$183.90	$183.90
Purchase #5	$44.68	7.870%	$48.1963	$48.20	$48.20	$48.20
Purchase #6	$100.61	10.565%	$111.2394	$111.24	$111.25	$111.20
Purchase #7	$11.28	7.159%	$12.0875	$12.09	$12.10	$12.10
7 purchase totals =	$659.16		$718.5601	$718.56	$718.55	$718.50