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	$88.94	10.374%	$98.1666	$98.17	$98.15	$98.20
Purchase #2	$153.89	13.467%	$174.6144	$174.61	$174.60	$174.60
Purchase #3	$118.25	13.163%	$133.8152	$133.82	$133.80	$133.80
Purchase #4	$205.63	4.854%	$215.6113	$215.61	$215.60	$215.60
Purchase #5	$109.66	12.247%	$123.0901	$123.09	$123.10	$123.10
Purchase #6	$98.61	10.617%	$109.0794	$109.08	$109.10	$109.10
Purchase #7	$58.25	6.703%	$62.1545	$62.15	$62.15	$62.20
7 purchase totals =	$833.23		$916.5315	$916.53	$916.50	$916.60